Portable industrial air filtration device

ABSTRACT

Various embodiments of the present disclosure provide a portable industrial air filtration device employing an annular dual filter assembly to capture and remove impurities from the air surrounding the air filtration device, enabling the air filtration device to quickly and efficiently improve the quality and safety of the air. The air filtration device includes a two-piece housing including a lower housing component and a locking cover removably attachable to the lower housing component. The dual filter assembly is mounted within the housing between the locking cover and the lower housing component, and includes a removable self-supporting outer pre-filter surrounding a separately removable inner HEPA filter. The pre-filter initially filters the surrounding air by capturing relatively large or coarse impurities, and the HEPA filter further filters the air pulled through the pre-filter by capturing relatively small or fine impurities.

PRIORITY CLAIM

This application is a continuation of, claims priority to and thebenefit of U.S. patent application Ser. No. 14/199,242, filed on Mar. 6,2014, which claims priority to and the benefit of U.S. ProvisionalPatent Application No. 61/789,190, filed on Mar. 15, 2013, the entirecontents of each are incorporated herein by reference.

BACKGROUND

Air filtration devices, also called air scrubbers, are well known andare used to remove impurities, such as particulates, from thesurrounding air. Typical air filtration devices include a fan assemblyand a filter assembly including one or more filters. Generally, whensuch an air filtration device is in operation, the fan assembly pulls orpushes air surrounding the air filtration device through the filterassembly, which captures and removes various impurities from the air.The filtered air is then expelled from the air filtration device.

One common use for air filtration devices is to filter the air in indooror otherwise enclosed construction sites. Various activities that occurin and around such enclosed construction sites cause the air in theconstruction sites to become filled with impurities such as dustparticles. For instance, many indoor construction projects, such as homeor business constructions or renovations, involve the installation ofdrywall. After drywall sheets are hung, drywall joint compound is thenapplied to fill any imperfections in the drywall (such as to cover thefasteners) and to fill seams between the hung drywall sheets. Thedrywall compound is then sanded, usually more than once, until it isflush with the drywall. Each instance of sanding causes copious amountsof fine particles of the drywall compound (and the drywall itself) to beexpelled into the air, creating clouds of drywall dust in the enclosedspace. The drywall dust makes it difficult for workers in theconstruction site to see what they are doing; puts the workers at riskfor various health problems, such as eye, nose, throat, and respiratorytract irritation and difficulty breathing; and eventually falls to theground, coating the workers, the construction site, and any tools andmaterials with a layer of drywall dust.

In another example, many indoor construction projects involve theinstallation of hardwood flooring. After the hardwood flooring is laid,the flooring is sanded, usually more than once. Each instance of sandingcauses copious amounts of fine particles of the flooring (i.e., thewood) to be expelled into the air, creating clouds of sawdust in theenclosed space. Similar to the drywall dust described above, the sawdustmakes it difficult for workers in the construction site to see what theyare doing; puts the workers at risk for various health problems, such aseye, nose, throat, and respiratory tract irritation and difficultybreathing; and eventually falls to the ground, coating the workers, theconstruction site, and any tools and materials with a layer of sawdust.Other common activities on such constructions sites, such as demolition(e.g., tearing down drywall and ripping up flooring); cutting variousmaterials such as wood, drywall, ceramic, concrete, stone, and plastics;drilling various materials such as wood, drywall, ceramic, concrete,stone, and plastics; and jack hammering concrete and stone, causesimilar problems.

Various precautions are used to protect against this kind ofparticulate-filled air. For example, workers are often required to wearprotective eye goggles or glasses to protect their eyes from theparticulates and nose and/or to wear face masks to reduce or inhibit theamount of the particulates they breathe in. As noted above, industrialair filtration devices are also typically used to filter the air in suchenclosed construction sites to attempt to improve the breathability andsafety of the air by removing some or all of these impurities.

While industrial air filtration devices are commonly used in suchconstruction sites, certain known industrial air filtration devices havea variety of disadvantages. Certain known industrial air filtrationdevices are large, bulky, heavy machines that are not easilytransportable to and from a construction site, around a constructionsite, or between construction sites, especially construction sites thatare indoors, oddly shaped, or otherwise enclosed. For instance, suchknown industrial air filtration devices are a chore to use in theconstruction or renovation of an office building containing hundreds oreven thousands of individual offices. Such known large, bulky, and heavyindustrial air filtration devices require workers to cart or otherwisetransport the devices around to each office on each floor, which addstime and expense to the project.

Certain known industrial air filtration devices operate at relativelyhigh fan speeds and include filters having relatively small surfaceareas. For such an industrial air filtration device, the combination ofthe relatively small filter surface areas, the relatively high fanspeed, and the relatively large size of the impurities captured by thefilters causes the filters to occlude quickly, which results indecreased performance (explained below) and the filters having to bereplaced often.

Many known industrial air filtration devices employ flat front filterassemblies. That is, such known industrial air filtration devicesinclude a filter assembly having one or more rectangular filters alongone side of the industrial air filtration device. Such an industrial airfiltration device employing a flat front filter assembly may filter airfrom one side of the industrial air filtration device (i.e., the side onwhich the filter assembly is located). This limits how quickly andefficiently the industrial air filtration device is able to filter theair surrounding the other sides of the air filtration device.

Many known industrial air filtration devices require users to manuallyinspect the filters to determine whether the filters should be replaced(i.e., to determine whether the filters are so occluded that theyrequire replacement to maintain efficient performance). This typicallyrequires a user to shut down such an industrial air filtration deviceand guess as to whether the filter(s) should be replaced. If the userincorrectly determines that a filter should be replaced, money is wastedin purchasing a new filter when the old filter is not completely usedup. This also adds to the environmental waste produced by the airfiltration device because the old filter is thrown away when it is notcompletely used up, and the packaging containing the new filter isthrown away when that new filter is not yet needed. If, on the otherhand, the user incorrectly determines that a filter should not bereplaced, the industrial air filtration device will not effectivelyfilter the air.

Many known industrial air filtration devices include two to threedistinct, manually controlled fan speed settings. As the filters of suchan industrial air filtration device occlude (i.e., as particulatesaccumulate on and in the filters), the rate of air flow through theindustrial air filtration device decreases. Filters are typicallyefficient for a narrow target range of rates of air flow through thefilters, and if the rate of air flow through the filters falls above orbelow that target range, the performance of the filters suffers. Thus,in such known industrial air filtration devices, a user must manuallychange the fan speed as the filters occlude to attempt to maintain therate of air flow through the filters within that target range. Becausethe industrial air filtration device only includes two to three distinctfan speed settings, in some instances the user may not be able toincrease the fan speed high enough to keep the rate of air flow throughthe industrial air filtration device within the target range. In otherinstances, however, the user may increase the fan speed too much,causing the rate of air flow through the industrial air filtrationdevice to fall outside of the target range.

Many known industrial air filtration devices require users to themselvesdetermine how much filtering the surrounding air requires and tomanually increase or decrease the fan speed of the industrial airfiltration devices accordingly. If the user incorrectly overestimatesthe speed at which such an industrial air filtration device should beoperating, unnecessary electricity costs accrue. If, on the other hand,the user incorrectly underestimates the speed at which the industrialair filtration device should be operating, the user and others in thevicinity will be exposed to (and breathe) air filled with potentiallydangerous impurities.

Many known industrial air filtration devices have no way ofautomatically determining whether the proper filters are installedand/or whether the proper number of filters are installed. This isproblematic because the industrial air filtration devices may notfunction properly to effectively filter the surrounding air if one ormore incorrect filters, such as incorrectly sized filters or filters ofthe wrong class or rating, are installed or if fewer than all of thefilters are installed.

Accordingly, there is a need for new and improved air filtration devicesthat overcome these disadvantages.

SUMMARY

Various embodiments of the present disclosure provide a portableindustrial air filtration device employing an annular dual filterassembly to capture and remove various impurities from the airsurrounding the portable industrial air filtration device, enabling theportable industrial air filtration device to quickly and efficientlyimprove the quality and safety of the air. In general, when the portableindustrial air filtration device is in operation, the portableindustrial air filtration device pulls (such as by drawing) airsurrounding the portable industrial air filtration device through theannular dual filter assembly, which captures and removes variousimpurities (such as particulates and other pollutants) from the air, andexpels the filtered, clean air out of the portable industrial airfiltration device. Thus, when the portable industrial air filtrationdevice is in operation, such as in an enclosed construction site mannedby a number of workers performing activities that cause particulates tofill the air, the portable industrial air filtration device continuouslyfilters and cleans the surrounding air, improving its breathability byreducing the amount of potentially dangerous impurities in the air.

In various embodiments, the portable industrial air filtration deviceincludes a two-piece housing including a lower housing component and alocking cover that is removably attachable to the lower housingcomponent. The dual filter assembly is mounted or installed within thehousing between the locking cover and the lower housing component. Thedual filter assembly includes a removable and replaceableself-supporting outer pre-filter surrounding a separately removable andreplaceable inner high-efficiency particulate air (HEPA) filter. Thepre-filter initially filters the surrounding air by capturing andremoving relatively large or coarse impurities from the air as the airis pulled through the pre-filter toward the HEPA filter. The pre-filtermedia includes a tacifier, which is a sticky substance that helps trapparticulates (such as dust) in the pre-filter media. The HEPA filterfurther filters the air pulled through the pre-filter by capturing andremoving relatively small or fine impurities from the air as the air ispulled through the HEPA filter toward the interior of the portableindustrial air filtration device. A user may access both filters (suchas to remove one or more of the filters) by detaching and removing thelocking cover from the lower housing component.

In various embodiments, the pre-filter is formed from two differentmaterials: pre-filter media, which forms the eventual exterior surfaceof the pre-filter, and a rigidized backing, which forms the eventualinterior surface of the pre-filter. The use of the rigidized backing incombination with the pre-filter media provides structural support to thepre-filter, rendering it rigid enough to support itself and stand on itsown without deforming, while maintaining enough flexibility to be packedflat for shipping and storage, which enables packaging materials andstorage space to be minimized. In one embodiment, the pre-filter isformed by placing the rigidized backing, which has upper and loweropposing edges and two opposing side edges, onto a sheet of thepre-filter media, which has upper and lower opposing edges and twoopposing side edges. The upper edge of the pre-filter media is foldedover the upper edge of the rigidized backing and heat sealed to hold itin place. Similarly, the lower edge of the pre-filter media is foldedover the lower edge of the rigidized backing and heat sealed to hold itin place.

This above process is repeated, resulting in two sheets of rigidizedpre-filter media. The pre-filter is formed by sewing the correspondingside edges of the two sheets of rigidized pre-filter media to oneanother to form an annular or ring-shaped structure such that the twosewed side seams run lengthwise down the height of the pre-filter, therigidized backing forms the interior surface of the pre-filter, and thepre-filter media forms the exterior surface of the pre-filter. Incertain embodiments, at least one surface of the pre-filter includes apre-filter sensor triggering component configured to trigger apre-filter sensor (such as a pre-filter limit switch actuator sized toactuate a pre-filter limit switch) when the pre-filter is properlyinstalled, which enables the portable industrial air filtration deviceto determine that an acceptable pre-filter is installed.

As described in detail below, the portable industrial air filtrationdevice of the present disclosure overcomes the above-explaineddisadvantages. The portable industrial air filtration device of variousembodiments of the present disclosure is a small, lightweight devicethat is easily transportable to and from a construction site, around aconstruction site, or between construction sites, especially those thatare indoors or otherwise enclosed. In one embodiment, the portableindustrial air filtration device is approximately 22 inches×22 inches×24inches (56 centimeters×56 centimeters×61 centimeters) (L×W×H) and weighsapproximately 40 pounds (18.1 kilograms). In comparison, one knownindustrial air filtration device is approximately 33 inches×32inches×25.5 inches (83.8 centimeters×81.3 centimeters×64.8 centimeters)(L×W×H) and weighs approximately 150 pounds (68 kilograms). Thus, unlikecertain known portable industrial air filtration devices, the portableindustrial air filtration device of the present disclosure is easilyliftable and transportable to and from a construction site, around aconstruction site, or between construction sites by a single worker.Further, the portable industrial air filtration device includes aplurality of stabilizers configured to guard the surfaces of the filtersfrom being inadvertently contacted, be used as handles to increasemaneuverability of the portable industrial air filtration device, andenable the portable industrial air filtration device to be positioned ina variety of different manners (such as upright or on its side).

Additionally, the annular dual filter assembly of the portableindustrial air filtration device of various embodiments of the presentdisclosure provides increased filter surface area compared to the filtersurface area of certain known industrial air filtration devicesemploying flat front filter assemblies. This increased surface areaenables the filters to last longer between filter changes and enablesthe portable industrial air filtration device of the present disclosureto filter more air than such known industrial air filtration devices inthe same amount of time.

The annular dual filter assembly of various embodiments of the portableindustrial air filtration device of the present disclosure also enablesthe portable industrial air filtration device to filter the airsurrounding the portable industrial air filtration device around thecircumference of the portable air filtration device rather than just onone side, as is the case with industrial air filtration devicesemploying flat front filter assemblies. This enables the portableindustrial air filtration device of the present disclosure to quicklyand efficiently filter the air surrounding the portable industrial airfiltration device.

The portable industrial air filtration device of various embodiments ofthe present disclosure monitors the occlusion of the filters (i.e., theamount of particulates accumulated on and in the filters). The portableindustrial air filtration device alerts the user when the filters havereached the ends of their useful lives and, therefore, should bereplaced. This enables users to quickly and easily determine how used upeach of the filters is and when the filters need replacement, therebyeliminating the time wasted manually checking each filter to determinewhether that filter is used up or not. This also eliminates the inherentguesswork as to whether or not a filter is used up, and the consequencescaused by guessing incorrectly (such as the increased environmental andmonetary waste).

The portable industrial air filtration device of various embodiments ofthe present disclosure employs dynamic fan speed control to adjust thefan speed to achieve a desired air flow rate through the air filtrationdevice. Generally, when employing dynamic fan speed control, the airfiltration device uses the pressure drop across the fan and the desiredair flow rate through the air filtration device to determine a desiredfan speed that achieves the desired flow rate through the air filtrationdevice. This enables the air filtration device to maintain that desiredair flow rate through the air filtration device by varying the fan speedas the pre-filter and the HEPA filter occlude during operation of theair filtration device, which prevents the air flow rate through the airfiltration device from falling below the desired air flow rate andimpairing the air filtration device's performance.

The portable industrial air filtration device of other embodiments ofthe present disclosure dynamically controls the speed of the fan of thefan assembly based on how occluded the filters are. This enables theportable industrial air filtration device to automatically adjust thefan speed as the filters occlude during operation to maintain a constantor substantially constant rate of air flow through the portableindustrial air filtration device within the target range for the filtersduring all phases of the filters' useful lives. This prevents the rateof air flow through the portable industrial air filtration device fromdecreasing and falling below the target range as the filter occludes,thereby ensuring proper and efficient performance throughout thefilters' useful lives and removing the guesswork inherent in requiring auser to manually adjust the fan speed.

The portable industrial air filtration device of various embodiments ofthe present disclosure includes an automatic fan speed setting selectionoperating mode. Generally, when the automatic fan speed settingselection operating mode is selected by the user, the air filtrationdevice uses a dust sensor to measure the amount of dust in the airsurrounding the air filtration device and, if necessary, automaticallyincreases or decreases the current fan speed setting to account for theamount of dust in the air. Thus, when operating in the automatic fanspeed setting selection operating mode, the air filtration devicedynamically and automatically adjusts the fan speed setting in real-timeto account for varying levels of dust in the air surrounding the airfiltration device, which eliminates the need for the user to guess theamount of dust in the air and manually select what the user believes tobe the most effective and efficient fan speed setting in which tooperate the air filtration device to remove that dust.

The portable industrial air filtration device of other embodiments ofthe present disclosure measures the amount of impurities in the air andautomatically increases or decreases fan speed when the amount ofimpurities reaches certain levels. This ensures that the portableindustrial air filtration device operates efficiently for the amount ofdust present in the environment, which eliminates the guesswork requiredto determine the speed at which to operate the portable industrial airfiltration device, eliminates electricity costs resulting frominefficient operation of the portable industrial air filtration device,and ensures worker safety.

The portable industrial air filtration device of various embodiments ofthe present disclosure detects when an acceptable pre-filter and anacceptable HEPA filter are installed, and does not enable the fan tooperate when an acceptable pre-filter is not installed and/or when anacceptable HEPA filter is not installed. This ensures that the portableindustrial air filtration device will work properly to effectivelyfilter and clean the surrounding air.

The portable industrial air filtration device of other embodiments ofthe present disclosure is also configured to detect when the properfilters are installed, and does not function when fewer than all of thefilters are installed (i.e., when only one filter is installed or whenno filters are installed) or when one or more improper filters areinstalled. This ensures that the portable industrial air filtrationdevice will work properly to effectively filter and clean thesurrounding air.

Additional features and advantages of the present invention aredescribed in, and will be apparent from, the following DetailedDescription and the Figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top perspective view of an embodiment of the portableindustrial air filtration device of the present disclosure.

FIG. 1B is a side view of the portable industrial air filtration deviceof FIG. 1A.

FIG. 1C is a top view of the portable industrial air filtration deviceof FIG. 1A.

FIG. 1D is a side cross-sectional view of the portable industrial airfiltration device of FIG. 1A taken substantially along line 1D-1D ofFIG. 1C, and illustrates the path of air flow through the portableindustrial air filtration device.

FIG. 1E is an exploded top perspective view of the portable industrialair filtration device of FIG. 1A.

FIG. 2A is a top perspective view of the lower housing component of theportable industrial air filtration device of FIG. 1A.

FIG. 2B is a bottom perspective view of the lower housing component ofFIG. 2A.

FIG. 2C is a top view of the lower housing component of FIG. 2A.

FIG. 2D is a bottom view of the lower housing component of FIG. 2A.

FIG. 2E is a side cross-sectional view of the lower housing component ofFIG. 2A taken substantially along line 2E-2E of FIGS. 2C and 2D.

FIG. 2F is a partial side cross-sectional view of the lower housingcomponent of FIG. 2A taken substantially along line 2E-2E of FIGS. 2Cand 2D.

FIG. 3 is a bottom perspective view of the fan assembly mounted to thefan assembly mounting bracket secured to the lower housing component ofthe portable industrial air filtration device of FIG. 1A.

FIG. 4A is a side perspective view of the exhaust screen of the portableindustrial air filtration device of FIG. 1A.

FIG. 4B is a front view of the exhaust screen of FIG. 4A.

FIG. 5A is a top perspective view of the filter assembly mountingchamber cover of the portable industrial air filtration device of FIG.1A.

FIG. 5B is a bottom perspective view of the filter assembly mountingchamber cover of FIG. 5A.

FIG. 6A is a top perspective view of the HEPA filter of the portableindustrial air filtration device of FIG. 1A without the protective mesh.

FIG. 6B is a top perspective view of the HEPA filter of FIG. 6A with theprotective mesh.

FIG. 6C is a side cross-sectional view of the HEPA filter of FIG. 6Btaken substantially along line 6C-6C of FIG. 6B.

FIG. 7 is a top perspective view of the HEPA filter securing bracket ofthe portable industrial air filtration device of FIG. 1A.

FIG. 8 is a top perspective view of the HEPA filter securing plate ofthe portable industrial air filtration device of FIG. 1A.

FIG. 9 is a partial side cross-sectional view of the portable industrialair filtration device of FIG. 1A taken substantially along line 1D-1D ofFIG. 1C.

FIG. 10A is a top perspective view of the pre-filter of the portableindustrial air filtration device of FIG. 1A.

FIG. 10B is a side cross-sectional view of the pre-filter of FIG. 10Ataken substantially along line 10B-10B of FIG. 10A.

FIG. 10C is a top perspective view of another example pre-filter.

FIG. 10D is a top perspective view of the pre-filter sensor triggeringcomponent of the pre-filter of FIG. 10A.

FIG. 11A is a top perspective view of the locking cover of the portableindustrial air filtration device of FIG. 1A.

FIG. 11B is a bottom perspective view of the locking cover of FIG. 11B.

FIG. 11C is a side cross-sectional view of the locking cover of FIG. 11Ataken substantially along line 11C-11C of FIG. 11A.

FIG. 12A is a top perspective view of another embodiment of the portableindustrial air filtration device of the present disclosure.

FIG. 12B is a side view of the portable industrial air filtration deviceof FIG. 12A.

FIG. 12C is another side view of the portable industrial air filtrationdevice of FIG. 12A.

FIG. 12D is another side view of the portable industrial air filtrationdevice of FIG. 12A.

FIG. 12E is another side view of the portable industrial air filtrationdevice of FIG. 12A.

FIG. 12F is a top view of the portable industrial air filtration deviceof FIG. 12A.

FIG. 12G is a bottom view of the portable industrial air filtrationdevice of FIG. 12A.

FIG. 12H is a side cross-sectional view of the portable industrial airfiltration device of FIG. 12A taken substantially along line 12H-12H ofFIG. 12F, and illustrates the path of air flow through the portableindustrial air filtration device.

FIG. 12I is an exploded top perspective view of the portable industrialair filtration device of FIG. 12A.

FIG. 13A is a top perspective view of the lower housing component of theportable industrial air filtration device of FIG. 12A.

FIG. 13B is a bottom perspective view of the lower housing component ofFIG. 13A.

FIG. 13C is a top view of the lower housing component of FIG. 13A.

FIG. 13D is a bottom view of the lower housing component of FIG. 13A.

FIG. 13E is a side cross-sectional view of the lower housing componentof FIG. 13A taken substantially along line 13E-13E of FIGS. 13C and 13D.

FIG. 13F is a partial side cross-sectional view of the lower housingcomponent of FIG. 13A taken substantially along line 13F-13F of FIGS.13C and 13D.

FIG. 14A is a top perspective view of the fan assembly mounting bracketof the portable industrial air filtration device of FIG. 12A.

FIG. 14B is a top view of the fan assembly mounting bracket of FIG. 14A.

FIG. 14C is a bottom view of the fan assembly mounting bracket of FIG.14A.

FIG. 14D is a side view of the fan assembly mounting bracket of FIG.14A.

FIG. 15 is a bottom perspective view of the fan assembly mounted to thefan assembly mounting bracket secured to the lower housing component ofthe portable industrial air filtration device of FIG. 12A.

FIG. 16A is a side perspective view of the exhaust screen of theportable industrial air filtration device of FIG. 12A.

FIG. 16B is a front view of the exhaust screen of FIG. 16A.

FIG. 17A is a top perspective view of the filter assembly mountingchamber cover of the portable industrial air filtration device of FIG.12A.

FIG. 17B is a bottom perspective view of the filter assembly mountingchamber cover of FIG. 17A.

FIG. 18A is a top perspective view of the air director of the portableindustrial air filtration device of FIG. 12A.

FIG. 18B is a top view of the air director of FIG. 18A.

FIG. 18C is a bottom view of the air director of FIG. 18A.

FIG. 18D is a side view of the air director of FIG. 18A.

FIG. 19A is a top perspective view of the HEPA filter of the portableindustrial air filtration device of FIG. 12A without the protectivemesh.

FIG. 19B is a top perspective view of the HEPA filter of FIG. 19A withthe protective mesh.

FIG. 19C is a side cross-sectional view of the HEPA filter of FIG. 19Btaken substantially along line 19C-19C of FIG. 19B.

FIG. 20A is a top perspective view of the HEPA filter securing bracketof the portable industrial air filtration device of FIG. 12A.

FIG. 20B is a side view of the HEPA filter securing bracket of FIG. 20A.

FIG. 21A is a top perspective view of the HEPA filter securing plate ofthe portable industrial air filtration device of FIG. 12A.

FIG. 21B is a side view of the HEPA filter securing plate of FIG. 21A.

FIG. 22 is a partial side cross-sectional view of the portableindustrial air filtration device of FIG. 12A taken substantially alongline 22-22 of FIG. 12F.

FIG. 23A is a top perspective view of the pre-filter of the portableindustrial air filtration device of FIG. 12A.

FIG. 23B is a side cross-sectional view of the pre-filter of FIG. 23Ataken substantially along line 23B-23B of FIG. 23A.

FIG. 23C is a top perspective view of another example pre-filter.

FIG. 23D is a top perspective view of the pre-filter limit switchactuator of the pre-filter of FIG. 23A.

FIG. 24A is a top perspective view of the locking cover of the portableindustrial air filtration device of FIG. 12A.

FIG. 24B is a bottom perspective view of the locking cover of FIG. 24B.

FIG. 24C is a side cross-sectional view of the locking cover of FIG. 24Ataken substantially along line 24C-24C of FIG. 24A.

FIG. 24D is the side cross-sectional view of FIG. 24C including thepre-filter and the HEPA filter.

FIG. 25 is a block diagram showing certain electronic components of theportable industrial air filtration device of FIG. 12A.

FIG. 26 illustrates a flowchart of one example embodiment of anautomatic fan speed setting selection process.

FIG. 27 illustrates a flowchart of one example embodiment of a dynamicfan speed control process.

FIG. 28 illustrates a flowchart of one example embodiment of apre-filter presence detection process.

FIG. 29 illustrates a flowchart of one example embodiment of a HEPAfilter presence detection process.

FIGS. 30A and 30B illustrate a flowchart of one example embodiment of afilter occlusion level monitoring process.

DETAILED DESCRIPTION A. First Example Embodiment

1. Components and Structure

Referring now to the drawings, FIGS. 1A, 1B, 1C, 1D, and 1E illustrateone example embodiment of the portable industrial air filtration deviceof the present disclosure, which is generally indicated by numeral 10and is sometimes referred to below as the air filtration device forbrevity. FIGS. 2A to 11C illustrate various components of the airfiltration device 10.

More specifically, FIGS. 1A, 1B, and 1C illustrate a top perspectiveview, a side view, and a top view, respectively, of the air filtrationdevice 10 in an assembled configuration; FIG. 1D illustrates a sidecross-sectional view of the air filtration device 10 taken substantiallyalong a vertical plane through line 1D-1D of FIG. 1C, and shows the pathair takes when passing through the air filtration device 10; and FIG. 1Eillustrates the air filtration device 10 in an exploded configuration.It should be appreciated that, for clarity, the Figures include asimplified illustration of the fan assembly 300.

The air filtration device 10 includes the following components, each ofwhich is described in detail below: (a) a two-piece housing including alower housing component 100 and a locking cover 200 that is removablyattachable to the lower housing component 100, (b) a fan assembly 300mounted within a fan assembly mounting chamber defined by an undersideof the lower housing component 100, (c) a fan assembly mounting chambercover 500 removably attachable to the underside of the lower housingcomponent 100 to substantially cover the fan assembly mounting chamberand enclose the fan assembly 300 within the fan assembly mountingchamber, (d) an exhaust screen 400 mounted to the lower housingcomponent 100 within an exhaust port, (e) a dual filter assembly mountedwithin the housing between the locking cover 200 and the lower housingcomponent 100 and including a removable and replaceable self-supportingouter pre-filter 900 surrounding a separately removable and replaceableinner HEPA filter 600, and (f) a HEPA filter securing plate 800 and aHEPA filter securing bracket 700 configured to operate with the HEPAfilter securing plate 800 to secure the HEPA filter 600 to the lowerhousing component 100.

As best illustrated in FIGS. 2A, 2B, 2C, 2D, 2E, and 2F, the lowerhousing component 100 includes a generally cylindrical base 110; aplurality of stabilizers 120, 130, and 140 circumferentially spacedapart around the base 110 and extending vertically from the base 110;and a half-ring shaped exhaust port upper portion 150 extendingtransversely from the base 110.

The base 110 includes a generally circular exterior top surface 111, aring-shaped exterior side surface 112, a ring-shaped interior sidesurface 116, a generally circular interior top surface 117, and aring-shaped bridging surface 115 bridging the exterior top surface 111and the interior top surface 117. The bridging surface 115 defines acircular fan assembly receiving opening through the center of the base110. The interior side surface 116 and the interior top surface 117define a fan assembly mounting chamber on the underside of the base 110.

As best shown in FIGS. 2A and 2C, in this example, the bridging surface115 includes two opposing HEPA filter mounting bracket mounting surfaces115 a and 115 b to which the HEPA filter mounting bracket 700 is secured(as described below). Additionally, as best shown in FIGS. 2B and 2D, inthis example, the interior side surface 116 of the base 110 includes twoopposing fan assembly mounting bracket mounting surfaces 116 a and 116 bto which the fan assembly mounting bracket 1000 is secured (as describedbelow). Further, as best shown in FIG. 2D, in this example the interiorside surface 116 includes a plurality of fan assembly mounting chambercover mounting surfaces 116 c circumferentially spaced apart around theinterior side surface 116 to which the fan assembly mounting chambercover 500 is secured (as described below).

In this illustrated example, the HEPA filter 600 is mounted to the base110 via a plurality of channels and surfaces (described in detail belowwith respect to FIG. 9). More specifically, as best shown in FIGS. 2Cand 2F, the exterior top surface 111 includes a plurality of firstconcave surfaces 111 a defining a plurality of first channels spacedaround the circumference of the exterior top surface 111 at a diameterDa. The exterior top surface 111 also includes a plurality of secondconcave surfaces 111 b defining a plurality of second channels spacedaround the circumference of the exterior top surface 111 at a diameterDb, which is larger than diameter Da. The exterior top surface 111 alsoincludes a generally flat HEPA filter mounting surface 111 c around thecircumference of the exterior top surface 111 at a diameter Dc. HEPAfilter mounting surface 111 c is recessed below first concave surfaces111 a and second concave surfaces 111 b of the exterior top surface 111.As described in detail below with respect to FIG. 9, the HEPA filter ismounted to the base via the HEPA filter mounting surface.

In this example, one of the first concave surfaces 111 a defines apressure sensor receiving opening 170 a therethrough, and one of thesecond concave surfaces 111 b defines a pressure sensor receivingopening 170 b therethrough. Each of the pressure sensor receivingopenings 170 a and 170 b is configured to receive and secure (such asvia a press fit or a friction fit) a pressure sensor (not shown) such asa pressure tube such that the pressure sensor is substantially flushwith its corresponding concave surface. In this example, as explainedbelow, the pressure sensor secured by the pressure sensor receivingopening 170 a is configured to measure the pressure on the interior ofthe portable air filtration device, while the pressure sensor secured bythe pressure sensor receiving opening 170 b is configured to measure thepressure between the pre-filter and the HEPA filter.

It should be appreciated that, in other embodiments, the exterior topsurface includes a single first concave surface defining a single firstchannel around the circumference of the exterior top surface at diameterDa. Similarly, in other embodiments, the exterior top surface includes asingle second concave surface defining a single second channel aroundthe circumference of the exterior top surface at diameter Db.

The pre-filter 900 is mounted to the base via a pre-filter mountingchannel. More specifically, as best shown in FIG. 2F, the exterior topsurface 111 includes a generally flat surface 111 d, an angled surface111 e, and a generally vertical surface 111 f that together define thering-shaped pre-filter mounting channel. As described below, thepre-filter is mounted to the base via the pre-filter mounting channel.

The stabilizers 120, 130, and 140 are configured to facilitate theattachment of the locking cover 200 to the lower housing component 100,to provide structural support for the air filtration device 10, and toprovide protection for the dual filter assembly. As best shown in FIGS.1D and 2E, the stabilizers 120, 130, and 140 are also configured suchthat they raise the air filtration device 10 off of the ground to allowfor air circulation under the air filtration device 10. While threestabilizers are employed in this example, it should be appreciated thatthe air filtration device may include any suitable quantity ofstabilizers.

More specifically, to facilitate the attachment of the locking cover 200to the lower housing component 110, in this example each of thestabilizers 120, 130, and 140 includes a locking cover mounting tab 121,131, and 141, respectively, and a latch mounting surface 129, 139, and149, respectively. The locking cover mounting tabs 121, 131, and 141 arereceived by the locking cover 200 (described below) and, once receivedby the locking cover 200, prevent the locking cover 200 from rotating.As shown in FIGS. 1A and 1B, a latch is mounted to each of the latchmounting surfaces 129, 139, and 149. The latches are attached tocorresponding integrated latching surfaces on the locking cover(described below) to secure the locking cover 200 to the lower housingcomponent 110.

In this example, side 143 of the stabilizer 140 includes a recessedcontrol panel mounting surface 144 to which an integrated control panel160 (shown in FIGS. 1A and 1B) is mounted. The control panel 160 enablesa user to control the operation of the air filtration device 10.Additionally, in this example, side 122 of the stabilizer 120 includes arecessed outlet panel mounting plate 123 to which an outlet panel 170(shown in FIG. 1D) is mounted. The outlet panel 170 includes a pluralityof electrical outlets 172 and an electrical cord 174 ending in a plug(not shown). To power the air filtration device 10, the user plugs theplug of the electrical cord 174 into a power source (such as a wallelectrical outlet). Once the air filtration device 10 is connected tothe power source, a user may operate the air filtration device 10 andmay plug other electronic devices into the electrical outlets 172 topower those devices.

The exhaust port upper portion 150 includes a convex exterior surface151 and a concave interior surface 152. The interior surface 152 of theexhaust port upper portion 150 includes two opposing exhaust screenmounting surfaces 152 a and 152 b to which the exhaust screen 400 ismounted (as described below).

In this example, the lower housing component is dual-walled androtationally molded out of plastic. It should be appreciated, however,that the lower housing component may be made of any suitable material ormaterials or manufactured in any suitable manner or manners.

As best illustrated in FIG. 3, the fan assembly 300 is mounted to thelower housing component 100 within the fan assembly mounting chamber viaa fan assembly mounting bracket 1000. More specifically, in thisillustrated example, the fan assembly mounting bracket 1000 is securedto the fan assembly mounting bracket mounting surfaces 116 a and 116 bof the interior side surface 116 of the base 110, and the fan assembly300 is mounted to the top side of the fan assembly mounting bracket 1000such that a portion of the fan assembly 300 is located within the fanassembly receiving opening through the center of the base 110 defined bythe connecting surface 115.

In this example, the fan assembly is a RadiCal centrifugal fanR2E250-RB02-15 available from ebmpapst, though it should be appreciatedthat any suitable fan assembly may be employed.

It should be appreciated that the fan assembly mounting bracket 1000 maybe secured to the fan assembly mounting bracket mounting surfaces of theinterior surface of the base in any suitable manner or manners, such asthrough the use of threaded fasteners. In this example, the fan assemblymounting bracket 1000 is a sheet metal bracket, though it should beappreciated that the fan assembly mounting bracket 1000 may be made ofany suitable material.

The exhaust screen 400, as best illustrated in FIGS. 4A and 4B, includesa plurality of exhaust screen mounting tabs 452 a and 452 b. The exhaustscreen 400 is mounted to the exhaust port upper portion 150 of the lowerhousing component 100 by securing the exhaust screen mounting tab 452 ato the exhaust screen mounting surface 152 a and the exhaust screenmounting tab 452 b to the exhaust screen mounting surface 152 b. Afterthe air filtration device is assembled, the exhaust screen is configuredto restrict access through the exhaust channel (described below) to themoving portions of the fan assembly.

In this illustrated embodiment, the exhaust screen 400 is mounted to theexhaust screen mounting surfaces 152 a and 152 b via threaded fasteners,though it should be appreciated that the exhaust screen may be mountedin any suitable manner. In this example, the exhaust screen 400 is aninjection molded plastic component. It should be appreciated, however,that the exhaust screen may be made of any suitable material ormaterials or manufactured in any suitable manner or manners.

As best illustrated in FIGS. 5A and 5B, the fan assembly mountingchamber cover 500 includes a circular portion 510 having a slightlyconcave interior surface 512 and a slightly convex exterior surface 514and an exhaust channel lower portion 520 extending transversely from thecircular portion 510 and having a concave interior surface 522 and aconvex exterior surface 524. The fan assembly mounting chamber cover 500is mounted to the base 110 via the fan assembly mounting chamber covermounting surfaces 116 c such that the fan assembly mounting chambercover 500 substantially covers the fan assembly mounting chamber andencloses the fan assembly 300 and the fan assembly mounting bracket 1000within the fan assembly mounting chamber. Once the fan assembly mountingchamber cover 500 is mounted to the base 110, the exhaust port upperportion 150 of the base 110 and the exhaust port lower portion 520 ofthe fan assembly mounting chamber cover 500 form an exhaust port thatdefines an exhaust channel.

In this example, the fan assembly mounting chamber cover 500 is a thinwalled plastic component, though it should be appreciated that the fanassembly mounting chamber cover may be made of any suitable material.

As best illustrated in FIGS. 6A, 6B, and 6C, the HEPA filter 600includes pleated HEPA filter media 610 sandwiched between upper andlower ring-shaped end caps 620 and 630, respectively. The HEPA filtermedia 610 and the upper and lower end caps 620 and 630 form or define acylindrical interior channel. As shown in FIGS. 6B and 6C, the HEPAfilter 600 also includes a protective mesh 640 covering the outer andinner surfaces of the HEPA filter media 610 around its entire outer andinner circumferences to protect the HEPA filter media 610. It should beappreciated that, for clarity, the protective mesh is not shown in FIG.6A.

The upper and lower end caps 620 and 630 each have an exterior diameterDe and an interior diameter Di. As best shown in FIG. 6C, the upper endcap 620 includes a first semi-circular surface 620 a defining a firstchannel around the circumference of the upper end cap 620 at diameterDa. The upper end cap 620 also includes a second semi-circular surface620 b defining a second channel around the circumference of the upperend cap 620 at diameter Db. The upper end cap 620 further includes agenerally flat mounting surface 620 c around the circumference of theupper end cap 620 at diameter Dc. The mounting surface 620 c is locatedbetween and raised above the first and second channels. Similarly, thelower end cap 630 includes a first semi-circular surface 630 a defininga first channel around the circumference of the lower end cap 630 atdiameter Da. The lower end cap 630 also includes a second semi-circularsurface 630 b defining a second channel around the circumference of thelower end cap 630 at diameter Db. The lower end cap 630 further includesa generally flat mounting surface 630 c around the circumference of thelower end cap 630 at diameter Dc. The mounting surface 630 c is locatedbetween and raised above the first and second channels.

The HEPA filter 600 is mounted to the lower housing component 100 and,more specifically, to the base 110, via the HEPA filter securing plate800 and the HEPA filter securing bracket 700. As best illustrated inFIG. 7, the HEPA filter securing bracket 700 includes two substantiallyvertical legs 711 and 712 connected by and extending downward from asubstantially horizontal brace 720 to form an inverted U-shape. The legs711 and 712 each include a HEPA filter securing bracket mounting tab 711a and 712 a, respectively, and the brace 720 includes a HEPA filtersecuring plate mounting surface 722. As best illustrated in FIG. 8, theHEPA filter securing plate 800 includes a disc having an upper surface810, a lower surface 820.

To mount the HEPA filter 600 to the lower housing component 100 and,more specifically, to the base 110, the HEPA filter securing bracket 700is first mounted to the base 110. More particularly, the HEPA filtersecuring bracket mounting tabs 711 a and 712 a are mounted to the HEPAfilter mounting bracket mounting surfaces 115 a and 115 b of the base110. After being mounted to the base 110, the brace 720 of the HEPAfilter securing bracket 700 is positioned above the center of the fanassembly receiving opening defined by the connecting surface 115.

The HEPA filter 600 is then mounted to the base 110 by positioning theHEPA filter 600 around the HEPA filter securing bracket 700 and restingthe lower end cap 630 of the HEPA filter 600 on the exterior top surface111 of the base 110. More specifically, as illustrated in FIG. 9, theHEPA filter 600 is mounted such that: (a) the first channel of the lowerend cap defined by the first surface 630 a of the lower end cap 630 ispositioned above the first channel defined by the first surface 111 a ofthe exterior top surface 111 of the base 110, (b) the second channel ofthe lower end cap defined by the second surface 630 b of the lower endcap 630 is positioned above the second channel defined by the secondsurface 111 b of the exterior top surface 111 of the base 110, and (c)the mounting surface 630 c of the lower end cap 630 abuts the HEPAfilter mounting surface 111 c of the exterior top surface 111 of thebase 110.

To secure the HEPA filter 600 to the lower housing component 100, theHEPA filter securing plate 800 is mounted atop the upper end cap 620 tothe HEPA filter securing plate mounting surface 722 of the brace 720 ofthe HEPA filter securing bracket 700. Once the HEPA filter securingplate 800 is mounted to the HEPA filter securing bracket 700, the HEPAfilter 600 is sandwiched between the HEPA filter securing plate 800 andthe base 110, thus ensuring that the HEPA filter 600 will not disengagefrom the base 110 until the HEPA filter securing plate 800 is removed.In this illustrated embodiment, the HEPA filter securing bracket ismounted to the lower housing component and the HEPA filter securingplate is mounted to the brace of the HEPA filter securing bracket usingthreaded fasteners, though it should be appreciated that the componentsmay be mounted in any suitable manner.

The mounting of the HEPA filter securing plate 800 to the HEPA filtersecuring bracket 700 causes the HEPA filter 600 and, more specifically,the mounting surface 630 c, to compress a gasket 190 located within themounting channel 111 c of the exterior top surface 111 of the base 110.This creates an airtight seal between the lower end cap 630 of the HEPAfilter 600 and the base 110.

In this illustrated example, both the upper and lower end caps of theHEPA filter include a specific geometry that enables airtight sealingwhen placed within the proper channel in the lower housing. As will beexplained in detail below, the specific end cap geometry and, morespecifically, the manner in which the end cap geometry enables anairtight seal to be formed, enables the air filtration device to sensewhether a proper HEPA filter is installed.

In this example, the end caps of the HEPA filter are molded urethane endcaps, though it should be appreciated that the end caps may be made ofany suitable material. While the end caps are substantially identical inthis example, it should be appreciated that in other embodiments theupper and lower end caps may have different geometries. Further, in thisexample, the protective mesh is a thin gage metal mesh, though it shouldbe appreciated that any suitable mesh may be employed.

FIGS. 10A and 10B illustrate the pre-filter 900. In various embodiments,the pre-filter 900 is formed from two different materials: pre-filtermedia and a rigidized backing. The use of the rigidized backing incombination with the pre-filter media provides structural support to thepre-filter, rendering it rigid enough to support itself and stand on itsown without deforming, while maintaining enough flexibility to be packedflat for shipping and storage, which enables packaging materials andstorage space to be minimized. In one embodiment, the pre-filter 900 isformed by placing the rigidized backing 920, which has upper and loweropposing edges and two opposing side edges, onto a sheet of thepre-filter media 915, which has upper and lower opposing edges and twoopposing side edges. The upper edge of the pre-filter media 915 isfolded over the upper edge of the rigidized backing 920 and heat sealedto hold it in place. The heat seals are generally indicated by numeral950. Similarly, the lower edge of the pre-filter media 915 is foldedover the lower edge of the rigidized backing 920 and heat sealed to holdit in place.

This above process is performed twice, resulting in two sheets ofrigidized pre-filter media 910 and 930. The pre-filter is formed bysewing the corresponding side edges of the two sheets of rigidizedpre-filter media 910 and 930 to one another to form an annular orring-shaped structure (as shown in FIG. 10A) or an oval or fish-eyestructure (as shown in FIG. 10C) such that the two sewed side seams 970a and 970 b run lengthwise down the full height of the pre-filter 900,the rigidized backing 920 and 940 forms the interior surface of thepre-filter 900, and the pre-filter media 915 and 935 forms the exteriorsurface of the pre-filter 900. The formed pre-filter 900 includes anupper edge formed by upper edges 912 and 932 of the sheets of rigidizedpre-filter media 910 and 930, and a lower edge formed by lower edges 914and 934 of the sheets of rigidized pre-filter media 910 and 930.

In this example, as shown in FIGS. 10A and 10D, the pre-filter includesa pre-filter sensor triggering component 990 (such as a plastic piece).The pre-filter sensor triggering component 990 includes a rectangularbase 991 and a pre-filter sensor triggerer 992 extending therefrom. Thebase 991 defines a plurality of attachment openings 993 therethrough. Inthis embodiment, the pre-filter sensor triggering component 990 isattached to the exterior of the pre-filter via the attachment openings993 (such as by sewing, adhesive, fastener, or any other suitable mannerof attachment) such that the pre-filter sensor triggerer 992 protrudesbelow the lower edge of the pre-filter 900 formed by the lower edges 914and 934 of the sheets of rigidized pre-filter material 910 and 930. Thepre-filter sensor triggering component 990 and, more specifically, thepre-filter sensor triggerer, is configured to trigger a pre-filtersensor, which enables the portable industrial air filtration device todetermine whether a proper pre-filter is installed. It should beappreciated that the pre-filter sensor triggering component may take anysuitable shape, be made of any suitable material, and attached at anysuitable location on the pre-filter.

In this example, the pre-filter media is a polyspun material, though itshould be appreciated that any suitable filter media may be employed.Additionally, in this example, the rigidized backing includes nylonmesh, though it should be appreciated that any suitable material may beemployed, such as a material including vertical, horizontal, or diagonalboning. In this example, the combination of the polyspun material andthe nylon mesh renders the pre-filter flexible enough to fold flat forshipping but rigid enough to support itself and to enable the pre-filterto be slid over and onto the HEPA filter. In other embodiments, a singlesheet of rigidized pre-filter media is created and formed into anannular or oval-shaped structure by sewing the two sides of that sheetof rigidized pre-filter media together. That is, in such embodiments,the formation of the pre-filter causes the pre-filter to include asingle seam. It should be appreciated that the sides of the rigidizedpre-filter media may be joined in any suitable manner other than or inaddition to sewing, such as by a heat seal or adhesive.

As best illustrated in FIGS. 11A and 11B, the locking cover 200 includesa generally circular base 210 including a handle 212 and a plurality ofmounts 220, 230, and 240 circumferentially spaced apart around the base210. Each of the mounts 220, 230, and 240 includes a generallycylindrical surface 221, 231, and 241, respectively, defining a lockingcover mounting tab receiving opening each configured to receive one ofthe locking cover mounting tabs of the stabilizers (described above).Additionally, each of the mounts 220, 230, and 240 includes anintegrated latching surface to facilitate the use of the latches mountedto the stabilizers.

To attach the locking cover 220 to the lower housing component 100, theuser positions the locking cover atop the stabilizers such that: thelocking cover mounting tab receiving opening defined by the surface 221of the mount 220 receives the locking cover mounting tab 121 of thestabilizer 120, the locking cover mounting tab receiving opening definedby the surface 231 of the mount 230 receives the locking cover mountingtab 131 of the stabilizer 130, and the locking cover mounting tabreceiving opening defined by the surface 241 of the mount 240 receivesthe locking cover mounting tab 141 of the stabilizer 140. The user thensecures each latch to its respective latch strike. Once secured to thelower housing component 100, the locking cover 200 secures thepre-filter 900 in place, and a user may carry or otherwise transport theair filtration device via the handle 212.

In this example, the locking cover is a rotationally molded plasticcomponent. It should be appreciated, however, that the locking cover maybe made of any suitable material or materials or manufactured in anysuitable manner or manners.

In another embodiment, the locking cover is attached to one of thestabilizers of the lower housing component via a hinge. Thus, in thisembodiment, the locking cover is not completely detachable from thelower housing component. Rather, to remove the filters in thisembodiment, the latches are unlocked and the locking cover is rotatedvia the hinge off of the lower housing component to provide access tothe filters. In other embodiments, the locking cover attaches to thestabilizers in any suitable manner, such as through the use of threadedfasteners.

2. Functions

Although not shown, the air filtration device of the present disclosureincludes a processor (such as a microprocessor) configured tocommunicate with and control various components of the air filtrationdevice (such as the fan assembly, the pressure sensors, and the controlpanel), as described below.

FIG. 1D illustrates the path air takes when passing through the airfiltration device. In operation, when the fan assembly is turned on, airsurrounding the air filtration device is pulled through the filterassembly into the interior cylindrical channel defined or formed by theHEPA filter. More specifically, the air is first pulled through thepre-filter, which initially filters the air by capturing and removingrelatively large or coarse impurities from the air as the air is pulledthrough the pre-filter toward the HEPA filter. The air is then pulledthrough the HEPA filter, which is configured to further filter the airby capturing and removing relatively small or fine impurities from theair as the air is pulled through the HEPA filter toward the interiorcylindrical channel. The filtered air exits the HEPA filter into theinterior cylindrical channel, and is then pulled into the fan assembly.The filtered air moves through and is pushed out of the fan assembly andthrough the exhaust channel, exiting the air filtration device.

In certain embodiments, the air filtration device is configured tomonitor the occlusion of the filters. Put differently, the airfiltration device is configured to monitor how clean the filters are.The air filtration device alerts the user to the cleanliness status ofeach of the filters, and when the filters have reached the ends of theiruseful lives and, therefore, should be replaced. This enables users toquickly and easily determine how “used up” each of the filters is andwhen each filter needs replacement. In one embodiment, the airfiltration device ceases to operate when one or more of the filtersreaches a designated level of occlusion. For example, the air filtrationdevice ceases to operate when at least one of the pre-filter and theHEPA filter is so occluded that it may not continue to efficientlyfilter the air.

In some embodiments, the air filtration device is configured todynamically control the speed of the fan of the fan assembly based onhow occluded the filters are. This enables the air filtration device toautomatically adjust the fan speed as the filters occlude duringoperation to maintain a constant or substantially constant rate of airflow through the air filtration device within the target range for thefilters during all phases of the filters' useful lives. This preventsthe rate of air flow through the air filtration device from decreasingand falling below the target range as the filters occlude, therebyensuring proper and efficient performance throughout the filters' usefullives.

In various embodiments, the air filtration device employs a plurality ofpressure sensors to monitor the occlusion of the filters, anddynamically controls the speed of the fan based on how occluded thefilters are. In one embodiment, the air filtration device includes twoindependent pressure sensors configured to measure the pressure dropacross each of the filters. More specifically, in this embodiment, theair filtration device includes a first pressure sensor configured tomeasure the pressure between the pre-filter and the HEPA filter, and asecond pressure sensor positioned on the interior of the HEPA filterconfigured to independently measure the pressure on the interior of theair filtration device.

In this embodiment, the air filtration device uses the differencebetween standard atmospheric pressure (i.e., 1 atmosphere or 100kilopascal) and the pressure measured by the first pressure sensor(i.e., the pressure drop across the pre-filter) to determine howoccluded the pre-filter is. Similarly, the air filtration device usesthe difference between the pressure measured by the first pressuresensor and the pressure measured by the second pressure sensor (i.e.,the pressure drop across the HEPA filter) to determine how occluded theHEPA filter is. The air filtration device uses this occlusioninformation to: (a) determine whether either of the filters needs to bereplaced, and (b) adjust the speed of the fan to maintain asubstantially constant rate of air flow through the air filtrationdevice that is within the target range for the filters. It should beappreciated that, in other embodiments, the air filtration deviceemploys at least one additional pressure sensor to measure the pressureof the air surrounding the air filtration device rather than assumingstandard atmospheric pressure. In certain embodiments, at least one ofthe first pressure sensor and the second pressure sensor is configuredto additionally measure ambient pressure.

In one embodiment, the air filtration device includes a pressure sensorconfigured to measure the pressure in the exhaust chamber, which enablesthe air filtration device to adapt to changes at the exhaust (such aswhen a duct is added).

In various embodiments, the air filtration device is configured toindicate to the user, such as via the control panel, when the filter orfilters need replacement. Additionally or alternatively, in someembodiments, the air filtration device is configured to indicate howoccluded each filter is at any given time, such as on a scale of notoccluded at all (e.g., a new filter) to completely occluded.

In this embodiment, the pressure sensors are Freescale +/−1.45 PSIMPXV7002DP sensors available from Freescale Semiconductor, though itshould be appreciated that any suitable pressure sensors or any othertypes of sensors may be employed.

In certain embodiments, the air filtration device employs a speed sensorto measure the fan's speed. In one such embodiment, the speed sensor isan optical sensor, though it should be appreciated that any suitablespeed sensor may be employed.

In various embodiments, the air filtration device is configured tomeasure the amount of impurities in the air and surrounding the airfiltration device and automatically modify the fan speed of the fanassembly in response to the amount of impurities present in the airimmediately surrounding the air filtration device. This ensures that theair filtration device operates efficiently. In one embodiment, the airfiltration device employs a Sharp GP2Y1010AU0F optical dust sensor tosense the level of impurities in the air surrounding the air filtrationdevice. It should be appreciated that any suitable sensor may beemployed to detect the amount of impurities in the air.

In certain embodiments, the air filtration device is configured todetect when the proper filters are installed, when the proper number offilters are installed, or both. In such embodiments, the air filtrationdevice does not function when one or more improper filters areinstalled; when fewer than all of the filters are installed (i.e., whenonly one filter is installed or when no filters are installed); or whenone or more improper filters are installed or when fewer than all of thefilters are installed. This ensures that the portable industrial airfiltration device will work properly to effectively filter and clean thesurrounding air.

In one embodiment, as described above, the pre-filter includes apre-filter sensor triggering component. The pre-filter sensor triggeringcomponent is configured to trigger a pre-filter sensor (such as a limitswitch) when the pre-filter is properly installed. This enables the airfiltration device to determine whether a proper pre-filter is installed.If the limit switch is not triggered, the air filtration devicedetermines that either no pre-filter is installed or an improperpre-filter is installed, and will not operate.

In another embodiment, the upper and lower edges of the pre-filter eachinclude an integrated metallic element (such as a 0.003 inch thick×1inch high element) that spans the pre-filter's circumference. In thisembodiment, the air filtration device includes a sensor (such as amagnet and Hall sensor) configured to detect the metallic element. Inthis embodiment, if the sensor does not detect any metallic element, theair filtration device determines that either no pre-filter is installedor an improper pre-filter is installed, and will not operate.

In another embodiment, the air filtration device is configured to usepressure sensors (as described above) to measure the pressure dropacross the pre-filter. In this embodiment, the pre-filter media ismodified such that the pressure drop across the pre-filter falls withina designated range that is different than (such as higher than) thepressure drop across a pre-filter employing non-modified pre-filtermedia. In this embodiment, if the measured pressure drop across thepre-filter is not within the designated range, the air filtration devicedetermines that either no pre-filter is installed or an improperpre-filter is installed, and will not operate.

In one embodiment, as described above, the HEPA filter includes end capshaving a specifically designed geometry that enables the HEPA filter toproperly seal against the base. In this embodiment, the air filtrationdevice includes a plurality of integrated pressure sensors (such asthose described above) configured to detect whether such an airtightseal is formed between the end cap and the base. If the pressure sensorsdo not detect such an airtight seal, the air filtration device will notoperate.

In another embodiment, the air filtration device is configured to usepressure sensors to measure the pressure drop across the HEPA filter. Inthis embodiment, the HEPA filter media is configured such that thepressure drop across the HEPA filter falls within a designated range.Here, if the measured pressure drop across the HEPA filter is not withinthe designated range, the air filtration device determines that eitherno HEPA filter is installed or an improper HEPA filter is installed, andwill not operate.

In another embodiment, the HEPA filter includes one or more integratedhollow pressure tubes positioned vertically among the pleats of the HEPAfilter media. An end of each of these pressure tubes is flush with thebottom of the lower HEPA filter end cap. In this embodiment, the airfiltration device includes one or more pressure sensors configured todetect the presence of the pressure tubes. Thus, in this embodiment, ifa HEPA filter without such pressure tubes is installed, the airfiltration device will determine that an improper HEPA filter isinstalled, and will not operate.

It should be understood that modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent disclosure, and it should be understood that this application isto be limited only by the scope of the appended claims.

B. Second Example Embodiment

1. Components and Structure

Referring now to the drawings, FIGS. 12A, 12B, 12C, 12D, 12E, 12F, 12G,12H, and 12I illustrate another example embodiment of the air filtrationdevice of the present disclosure, which is generally indicated bynumeral 2010. FIGS. 13A to 24D illustrate the various components of theair filtration device 2010 generally shown in FIG. 12I, which is anexploded view of the air filtration device 2010. It should beappreciated that, for clarity, the Figures include a simplifiedillustration of the fan assembly 2300.

As best shown in FIG. 12I, the air filtration device 2010 includes thefollowing components, each of which is described in detail below: (a) atwo-piece housing including a lower housing component 2100 and a lockingcover 2200 that is removably attachable to the lower housing component2100, (b) a fan assembly mounting bracket 3000 attached to the lowerhousing component 2100 within a fan assembly mounting chamber defined byan underside of the lower housing component 2100, (c) a fan assembly2300 attached to the fan assembly mounting bracket 3000, (d) a fanassembly mounting chamber cover 2500 attached to the underside of thelower housing component 2100 to substantially cover the fan assemblymounting chamber and enclose the fan assembly mounting bracket 3000 andthe fan assembly 2300 within the fan assembly mounting chamber, (e) anexhaust screen 2400 positioned within an exhaust port formed by thelower housing component 2100 and the fan assembly mounting chamber cover2500, (f) an air director 3100 attached to the lower housing component2100 upstream of the fan assembly 2300, (g) a dual filter assemblyinstalled within the housing between the locking cover 2200 and thelower housing component 2100 and including a removable and replaceableself-supporting outer pre-filter 2900 surrounding a separately removableand replaceable inner HEPA filter 2600, (h) a HEPA filter securingbracket 2700 attached to the lower housing component 2100, and (i) aHEPA filter securing plate 2800 attached to the HEPA filter securingbracket 2800 that secures the HEPA filter 2600 to the lower housingcomponent 2100.

FIG. 12H generally illustrates the path air takes when passing throughthis example embodiment of the air filtration device 2010. In operation,air surrounding the air filtration device is drawn through the dualfilter assembly into the interior cylindrical channel defined or formedby the HEPA filter. More specifically, the air is first drawn throughthe pre-filter, which initially filters the air by capturing andremoving relatively large or coarse impurities from the air as the airis drawn through the pre-filter toward the HEPA filter. The air is thendrawn through the HEPA filter, which further filters the air bycapturing and removing relatively small or fine impurities from the airas the air is drawn through the HEPA filter toward the interiorcylindrical channel. The filtered air exits the HEPA filter into theinterior cylindrical channel, and is then drawn through the airdirector, which directs the filtered air into the fan assembly. The fandraws the filtered air into the fan assembly and expels the air from thefan assembly and through the exhaust channel, exiting the air filtrationdevice.

As best illustrated in FIGS. 13A, 13B, 13C, 13D, 13E, and 13F, the lowerhousing component 2100 includes: (a) a base 2110; (b) a plurality ofstabilizers 2120, 2130, and 2140 extending vertically from andcircumferentially spaced apart around the base 2110 (with respect to theorientation shown in FIGS. 13E and 13F); and (c) an exhaust port upperportion 2150 extending transversely from the base 2110.

The base 2110 includes: (a) a generally cylindrical exterior sidesurface 2112 to which the stabilizers 2120, 2130, and 2140 are attached;(b) a generally annular exterior upper surface including a plurality ofsurfaces to which various other components of the air filtration deviceare mounted (described below); (c) a generally cylindrical interior sidesurface 2116 a; and (d) a generally annular interior upper surface 2116b. The interior side surface 2116 a and the interior top surface 2116 bgenerally define a fan assembly mounting chamber on the underside of thebase 2110.

Turning to the exterior of the base 2110, as best shown in FIGS. 13A and13C, the exterior upper surface of the base 2110 includes a generallyannular air director mounting surface 2115 to which the air director3100 is attached (described below). In this example embodiment, the airdirector mounting surface 2115 includes four sections: (a) first andsecond opposing sections 2115 b and 2115 d, and (b) third and fourthopposing sections 2115 a and 2115 c. In this example embodiment, thefirst and second sections 2115 b and 2115 d are recessed with respect tothe third and fourth sections 2115 a and 2115 c (with respect to theorientation shown FIG. 13C).

In this example embodiment, the base 2110 defines fastener receivingopenings 2114 a, 2114 b, 2114 c, and 2114 d at least partiallytherethrough. The fastener receiving opening 2114 a is partially definedthrough the third section 2115 a of the air director mounting surface2115, the fastener receiving opening 2114 b is partially defined throughthe first section 2115 c of the air director mounting surface 2115, thefastener receiving opening 2114 c is partially defined through thefourth section 2115 c of the air director mounting surface 2115, and thefastener receiving opening 2114 d is partially defined through thesecond section 2115 d of the air director mounting surface 2115. Itshould be appreciated that the fastener receiving openings 2114 aresubstantially equally circumferentially spaced around a vertical axisthrough the center of the base 2110.

As best shown in FIGS. 13A, 13C, 13E, and 13F, the exterior uppersurface of the base 2110 includes a surface 2111 b having a “V-shaped”cross-section that defines a pre-filter securing channel around avertical axis through the center of the base 2110. The base 2110 definesa pre-filter limit switch actuator receiving opening 2175 at leastpartially therethrough. The pre-filter limit switch actuator ispartially defined through the surface 2111 b, and is sized to receive apre-filter limit switch actuator of the pre-filter 2900 (describedbelow). Generally, the base 2110 supports a pre-filter limit switch (notshown) that is actuatable by the pre-filter limit switch actuator of thepre-filter 2900, and the pre-filter limit switch actuator receivingopening 2175 enables the pre-filter limit switch actuator to actuate thepre-filter limit switch when the pre-filter 2900 is installed.

As also best shown in FIGS. 13A, 13C, 13E, and 13F, the exterior uppersurface of the base 2110 includes a plurality of annular surfaces 2111 dand 2111 f that are connected by an upwardly-protruding sealing rib 2111e (with respect to the orientation shown in FIGS. 13E and 13F).Together, the surfaces 2111 d and 2111 f and the sealing rib 2111 e forma HEPA filter mounting channel around a vertical axis through the centerof the base 2110.

As also best shown in FIGS. 13A, 13C, 13E, and 13F, the exterior uppersurface of the base 2110 includes an annular surface 2111 c bridging thepre-filter securing channel and the HEPA filter mounting channel and anannular surface 2111 g partially bridging the HEPA filter mountingchannel and the air director mounting surface 2115. The base 2110defines a pressure sensor port 2170 b at least partially therethrough towhich one or more pressure sensors may be attached to measure thepressure between the pre-filter and the HEPA filter, as described below.The base 2110 also defines a pressure sensor port 2170 a at leastpartially therethrough to which one or more pressure sensors may beattached to measure the pressure downstream of the HEPA filter andupstream of the fan assembly, as described below. The pressure sensorport 2170 b is partially defined through the surface 2111 c, and thepressure sensor port 2170 a is partially defined through the surface2111 g.

Turning to the interior of the base 2110, as best shown in FIGS. 13B and13D, the interior side surface 2116 a of the base 2110 includes threefan assembly mounting bracket mounting surfaces 2117 a, 2117 b, and 2117c extending inwardly therefrom (with respect to the orientation shown inFIG. 13D) to which the fan assembly mounting bracket 3000 is attached(described below). As best shown in FIG. 13D, the interior side surface2116 a includes a plurality of fan assembly mounting chamber covermounting surfaces 2118 spaced apart around the interior side surface2116 a and extending inwardly therefrom (with respect to the orientationshown in FIG. 13D) to which the fan assembly mounting chamber cover 2500is attached (described below). The interior side surface 2116 a alsodefines a pressure sensor port 2119 at least partially therethrough towhich one or more pressure sensors may be attached to measure thepressure downstream of the fan assembly, as described below.

The stabilizers 2120, 2130, and 2140 facilitate attachment of thelocking cover 2200 to the lower housing component 2100, providestructural support for the air filtration device 2010, and provideprotection for the dual filter assembly. Additionally, as best shown inFIGS. 12B, 12C, 12D, 12E, and 13E, the stabilizers raise the airfiltration device off of the ground to enable air to circulate under theair filtration device. While the air filtration device includes threestabilizers in this example embodiment, it should be appreciated thatthe air filtration device may include any suitable quantity ofstabilizers.

To facilitate attachment of the locking cover 2200 to the lower housingcomponent 2110, in this example embodiment, each of the stabilizers2120, 2130, and 2140 includes a locking cover mounting tab 2121, 2131,and 2141, respectively, and a latch mounting surface 2129, 2139, and2149, respectively. The locking cover mounting tabs 2121, 2131, and 2141are received by the locking cover 2200 (described below) and,thereafter, prevent the locking cover 2200 from rotating with respect tothe lower housing component 2100. As shown in FIGS. 12A, 12B, 12C, 12D,12D, and 12F, a latch is mounted to each of the latch mounting surfaces2129, 2139, and 2149. The latches are attached to correspondingintegrated latch strikes on the locking cover 2200 (described below) tosecure the locking cover 2200 to the lower housing component 2110.

In this example embodiment, side 2143 of the stabilizer 2140 includes arecessed control panel mounting surface 2144 to which an integratedcontrol panel 2160 is attached. The control panel 2160, which is shownin FIGS. 12A and 12B, enables the user to select a desired operatingmode of the air filtration device and provides information regarding thestatus of the air filtration device and the filters. In this exampleembodiment, the control panel 2160 includes or is otherwise associatedwith: (i) an operating mode selector 2161; (ii) a plurality of operatingmode indicators 2161 a, 2161 b, 2161 c, 2161 d, and 2161 e that eachindicate or identify one of the operating modes of the air filtrationdevice (described below); (iii) a pre-filter fault indicator 2162; (iv)a plurality of pre-filter status indicators 2163; (v) a HEPA filterfault indicator 2164; (vi) a plurality of HEPA filter status indicators2165; (vii) an air filtration device status indicator 2166; (viii) anhour meter display 2167; and (ix) a dust sensor receiving port 2168 intowhich a dust sensor (not shown) is fit. It should be appreciated thateach of these components is described in detail below with respect toFIGS. 25, 26, 27, 28, 29, and 30.

Additionally, in this example embodiment, side 2122 of the stabilizer2120 includes a recessed power panel mounting surface 2123 to which apower panel 2170 is attached. The power panel 2170, which is shown inFIG. 12E, includes: (a) a plurality of electrical outlets 2172, (b) apower switch 2176 having “ON” and “OFF” positions, and (c) a strainrelief bushing 2174 for a power cord that ends in a plug (not shown). Inthis example embodiment, to power the air filtration device 2010, theuser plugs the plug of the power cord into an A/C power source (such asa wall electrical outlet), and switches the power switch 2176 to the“ON” position. To cut power to the air filtration device 2010, the usereither unplugs the plug of the power cord from the A/C power source orswitches the power switch 2176 to the “OFF” position. In this exampleembodiment, once the air filtration device 2010 is connected to the A/Cpower source via the plug of the power cord, the electrical outlets 2172are powered and the user may plug other electronic devices into theelectrical outlets 2172 to power those electronic devices.

It should be appreciated that, in other embodiments, the air filtrationdevice includes fewer electrical outlets, more electrical outlets, or noelectrical outlets. In other embodiments, the air filtration device isoperable using any suitable power source other than and/or in additionto an A/C power source, such as one or more replaceable or rechargeablebatteries.

As best shown in FIGS. 13C and 13D, the exhaust port upper portion 2150extends transversely from the base such that the exhaust port upperportion 2150 is substantially parallel to a plane extending between thestabilizers 2120 and 2130. The exhaust port upper portion 2150 includesa convex exterior surface 2151 and a concave interior surface 2152. Theinterior surface 2152 of the exhaust port upper portion 2150 includestwo exhaust screen mounting surfaces 2154 and 2155 to which the exhaustscreen 2400 is attached (described below). The base 2110 definesfastener receiving openings 2154 a and 2155 a at least partiallytherethrough. The fastener receiving opening 2154 a is partially definedthrough the exhaust screen mounting surface 2154 and the fastenerreceiving opening 2155 a is partially defined through the exhaust screenmounting surface 2155. The base also defines an exhaust screen mountingchannel 2153 partially through the interior surface 2152 of the exhaustport upper portion 2150.

In this example embodiment, the lower housing component is dual-walledand rotationally molded out of plastic. It should be appreciated,however, that the lower housing component may be made of any suitablematerial(s) or manufactured in any suitable manner(s).

As best illustrated in FIGS. 14A, 14B, 14C, and 14D the fan assemblymounting bracket 3000 includes: (a) a generally rectangular fan assemblymounting bracket body 3010 defining: (i) a fastener receiving opening3012 therethrough proximate each corner of the fan assembly mountingbracket body 3010, (ii) a fan assembly receiving opening 3040therethrough proximate the center of the fan assembly mounting bracketbody 3010, (iii) a plurality of fastener receiving openings 3042therethrough spaced around the fan assembly receiving opening 3040, and(iv) a fan motor capacitor fastener receiving opening 3032 therethrough;(b) generally rectangular flanges 3070 and 3080 extending substantiallyperpendicularly in a first direction from opposing edges of the fanassembly mounting bracket body 3010; (c) a fan motor capacitor mountingbracket 3030 extending substantially perpendicularly in the firstdirection from the fan assembly mounting bracket body 3010; and (d) afan speed sensor mounting bracket 3020 extending substantiallyperpendicularly in a second direction, which is opposite the firstdirection, from the fan assembly mounting bracket body 3010. In thisexample embodiment, the fan assembly mounting bracket 3000 is made ofsheet metal, though it should be appreciated that the fan assemblymounting bracket may be made of any suitable material.

As best illustrated in FIGS. 16A and 16B, the exhaust screen 2400includes a plurality of exhaust screen mounting tabs 2454 and 2455 and aflange 2453 spanning the exhaust screen mounting tabs. The exhaustscreen mounting tab 2454 includes a base mounting surface 2454 a and anopposing fan assembly mounting chamber cover mounting surface 2454 b anddefines a fastener receiving opening 2456 therethrough. Similarly, theexhaust screen mounting tab 2455 includes a base mounting surface 2455 aand an opposing fan assembly mounting chamber cover mounting surface2455 b and defines a fastener receiving opening 2457 therethrough.

In this example embodiment, the exhaust screen 2400 is an injectionmolded plastic component. It should be appreciated, however, that theexhaust screen may be made of any suitable material or materials ormanufactured in any suitable manner or manners.

As best illustrated in FIGS. 17A and 17B, the fan assembly mountingchamber cover 2500 includes: (a) a circular portion 2510 having aslightly concave interior surface 2512 and a slightly convex exteriorsurface 2514, and (b) an exhaust channel lower portion 2520 extendingtransversely from the circular portion 2510 and having a concaveinterior surface 2522 and a convex exterior surface 2524. The circularportion defines a plurality of fastener receiving openings 2154therethrough. The exhaust channel lower portion 2520 includes twoexhaust screen mounting surfaces 2554 and 2555 to which the exhaustscreen 2400 is attached (described below). The exhaust channel lowerportion 2520 defines fastener receiving openings 2524 a and 2524 btherethrough. The fastener receiving opening 2524 a is partially definedthrough the exhaust screen mounting surface 2554 and the fastenerreceiving opening 2524 b is partially defined through the exhaust screenmounting surface 2555.

In this example embodiment, the fan assembly mounting chamber cover 2500is a thin walled plastic component, though it should be appreciated thatthe fan assembly mounting chamber cover may be made of any suitablematerial.

As best illustrated in FIGS. 18A, 18B, 18C, and 18D, the air director3100 includes: (a) an annular portion 3110, (b) a bridging portion 3120extending downwardly and inwardly from the inner edge of the annularportion 3110 (with respect to the orientation shown in FIG. 18D), and(c) a ring-shaped portion 3130 extending downwardly from the inner edgeof the bridging portion 3120 (with respect to the orientation shown inFIG. 18D).

The annular portion 3110 defines fastener receiving openings 3110 a,3110 b, 3110 c, and 3110 d therethrough. In this example embodiment, thefastener receiving openings 3110 a, 3110 b, 3110 c, and 3110 d aresubstantially equally circumferentially spaced around a vertical axisthrough the center of the annular portion 3110. As best shown in FIGS.18A and 18B, the air director 3100 includes rectangular HEPA filtermounting bracket mounting surfaces 3112 a and 3114 a proximate thefastener receiving openings 3110 b and 3110 d, respectively. It shouldbe appreciated that the HEPA filter mounting bracket mounting surfaces3112 a and 3114 a are recessed relative to the annular portion 3110(with respect to the orientation shown in FIG. 18D). As best shown inFIG. 18C, the air director 3100 includes rectangular air directormounting surfaces 3112 b and 3114 b, which are opposite the HEPA filtermounting bracket mounting surfaces 3112 a and 3114 a, respectively.

As best illustrated in FIGS. 19A, 19B, and 19C, the HEPA filter 2600includes pleated HEPA filter media 2610 sandwiched between upper andlower ring-shaped end caps 2620 and 2630, respectively. The HEPA filtermedia 2610 and the upper and lower end caps 2620 and 2630 form or definea cylindrical interior channel. As shown in FIG. 19B and 19C, the HEPAfilter 2600 also includes a protective mesh 2640 covering the outer andinner surfaces of the HEPA filter media 2610 around its entire outer andinner circumferences to protect the HEPA filter media 2610. It should beappreciated that, for clarity, the protective mesh is not shown in FIG.19A.

The upper and lower end caps 2620 and 2630 each have an exteriordiameter De and an interior diameter Di. As best shown in FIG. 19C, theupper end cap 2620 includes a first surface 2620 a having asemi-circular cross-section that defines a first channel around thecircumference of the upper end cap 2620 at diameter Da. The upper endcap 2620 also includes a second surface 2620 b having a semi-circularcross-section defining a second channel around the circumference of theupper end cap 2620 at diameter Db. The upper end cap 2620 furtherincludes a generally flat mounting surface 2620 c around thecircumference of the upper end cap 2620 at diameter Dc. The mountingsurface 2620 c is located between and above (with respect to theorientation shown in FIG. 19C) the first and second channels. Similarly,the lower end cap 2630 includes a first surface 2630 a having asemi-circular cross-section that defines a first channel around thecircumference of the lower end cap 2630 at diameter Da. The lower endcap 2630 also includes a second surface 2630 b having a semi-circularcross-section that defines a second channel around the circumference ofthe lower end cap 2630 at diameter Db. The lower end cap 2630 furtherincludes a generally flat mounting surface 2630 c around thecircumference of the lower end cap 2630 at diameter Dc. The mountingsurface 2630 c is located between and below (with respect to theorientation shown in FIG. 19C) the first and second channels.

In this example embodiment, both the upper and lower end caps of theHEPA filter include a specific geometry that enables airtight sealingwhen the HEPA filter is installed. As will be explained in detail below,this specific end cap geometry and, more specifically, the manner inwhich the end cap geometry enables an airtight seal to be formed,enables the air filtration device to accurately measure variouspressures and perform certain functions using those measured pressures.In this example embodiment, the end caps of the HEPA filter are made ofmolded urethane, though it should be appreciated that the end caps maybe made of any suitable material. While the end caps are substantiallyidentical in this example embodiment, it should be appreciated that inother embodiments the upper and lower end caps may have differentgeometries. Further, in this example embodiment, the outer protectivemesh is made of plastic and the inner protective mesh is made of a thingage metal, though it should be appreciated that the protective mesh maybe made of any suitable material.

As best illustrated in FIGS. 20A and 20B, the HEPA filter securingbracket 2700 includes: (a) a rectangular brace 2710, (b) a first leg2720 connected to and extending down and away from a first edge of thebrace 2710 (with respect to the orientation shown in FIG. 20B), (c) asecond leg 2730 connected to and extending down and away from a secondedge of the brace 2710 that is opposite the first edge (with respect tothe orientation shown in FIG. 20B), (d) a first HEPA filter securingbracket mounting tab 2740 that is substantially parallel to the brace2710 and extends away from the edge of the first leg 2720 opposite theedge connected to the first edge of the brace 2710, and (e) a secondHEPA filter securing bracket mounting tab 2750 that is substantiallyparallel to the brace 2710 and extends away from the edge of the secondleg 2723 opposite the edge connected to the second edge of the brace2710.

The brace 2710 includes an annular, downwardly embossed HEPA filtersecuring plate nesting surface 2712 (with respect to the orientationshown in FIG. 20B) that defines a nut receiving opening 2712 atherethrough. The nut receiving opening 2712 a includes an integratednut 2715 that defines a HEPA filter securing plate fastener receivingopening 2715 a therethrough. The first and second HEPA filter securingbracket mounting tabs 2740 and 2750 each define HEPA filter securingbracket fastener receiving openings 2740 a and 2750 a, respectively,therethrough.

As best illustrated in FIGS. 21A and 21B, the HEPA filter securing plate2800 includes: (a) a first annular portion 2810, (b) a flange 2815extending upwardly from an outer edge of the first annular portion 2810around the circumference of the outer edge of the first annular portion2810 (with respect to the orientation shown in FIG. 21B), (c) a firstannular bridging portion 2820 extending downwardly and inwardly from theinner edge of the first annular portion 2810 (with respect to theorientation shown in FIG. 21B), (d) a second annular portion 2830connected to and extending inwardly from the first annular bridgingportion 2820 (with respect to the orientation shown in FIG. 21B), (e) asecond annular bridging portion 2840 extending downwardly and inwardlyfrom the inner edge of the second annular portion 2830 (with respect tothe orientation shown in FIG. 21B), and (f) a third annular portion 2850extending inwardly from the second annular bridging portion 2840 (withrespect to the orientation shown in FIG. 21B). The third annular portion2850 defines a fastener receiving opening 2850 a therethrough.

FIGS. 23A and 23B illustrate the pre-filter 2900. In variousembodiments, the pre-filter 2900 is formed from two different materials:pre-filter media and a rigidized backing. The use of the rigidizedbacking in combination with the pre-filter media provides structuralsupport to the pre-filter, rendering it rigid enough to support itselfand stand on its own without deforming, while maintaining enoughflexibility to be packed flat for shipping and storage, which enablespackaging materials and storage space to be minimized. In oneembodiment, the pre-filter 2900 is formed by placing the rigidizedbacking 2920, which has upper and lower opposing edges and two opposingside edges, onto a sheet of the pre-filter media 2915, which has upperand lower opposing edges and two opposing side edges. The upper edge ofthe pre-filter media 2915 is folded over the upper edge of the rigidizedbacking 2920 and heat sealed to hold it in place. The heat seals aregenerally indicated by numeral 2950. Similarly, the lower edge of thepre-filter media 2915 is folded over the lower edge of the rigidizedbacking 2920 and heat sealed to hold it in place.

This above process is performed twice, resulting in two sheets ofrigidized pre-filter media 2910 and 2930. The pre-filter is formed bysewing the corresponding side edges of the two sheets of rigidizedpre-filter media 2910 and 2930 to one another to form an annular orring-shaped structure (as shown in FIG. 23A) or an oval or fish-eyestructure (as shown in FIG. 23C) such that the two sewed side seams 2970a and 2970 b run lengthwise down the full height of the pre-filter 2900,the rigidized backing 2920 and 2940 forms the interior surface of thepre-filter 2900, and the pre-filter media 2915 and 2935 forms theexterior surface of the pre-filter 2900. The formed pre-filter 2900includes an upper edge formed by upper edges 2912 and 2932 of the sheetsof rigidized pre-filter media 2910 and 2930, and a lower edge formed bylower edges 2914 and 2934 of the sheets of rigidized pre-filter media2910 and 2930.

In this example embodiment, as shown in FIGS. 23A and 23D, thepre-filter includes a pre-filter limit switch actuator 2990 (such as aplastic piece). The pre-filter limit switch actuator 2990 includes arectangular base 2991 and an actuator 2992 extending therefrom. The base2991 defines a plurality of attachment openings 2993 therethrough. Inthis embodiment, the pre-filter limit switch actuator 2990 is attachedto the exterior of the pre-filter via the attachment openings 2993 (suchas by sewing, adhesive, fastener, or any other suitable manner ofattachment) such that the pre-filter limit switch actuator 2992 extendsbelow the lower edge of the pre-filter 2900 formed by the lower edges2914 and 2934 of the sheets of rigidized pre-filter material 2910 and2930. The pre-filter sensor limit switch actuator 2990 is sized toactuate the pre-filter limit switch, as described above, which enablesthe air filtration device to determine whether an acceptable pre-filteris installed. It should be appreciated that the pre-filter limit switchactuator may take any suitable shape, be made of any suitable material,and attached at any suitable location on the pre-filter, such as theinterior of the pre-filter.

In this example embodiment, the pre-filter media is a polyspun material,though it should be appreciated that any suitable filter media may beemployed. Additionally, in this example embodiment, the rigidizedbacking includes nylon mesh, though it should be appreciated that anysuitable material may be employed, such as a material includingvertical, horizontal, or diagonal boning. In this example embodiment,the combination of the polyspun material and the nylon mesh renders thepre-filter flexible enough to fold flat for shipping but rigid enough tosupport itself and to enable the pre-filter to be slid over and onto theHEPA filter. In other embodiments, a single sheet of rigidizedpre-filter media is created and formed into an annular or oval-shapedstructure by sewing the two sides of that sheet of rigidized pre-filtermedia together. That is, in such embodiments, the formation of thepre-filter causes the pre-filter to include a single seam. It should beappreciated that the sides of the rigidized pre-filter media may bejoined in any suitable manner other than or in addition to sewing, suchas by a heat seal or adhesive.

As best illustrated in FIGS. 24A, 24B, 24C, and 24D, the locking cover2200 includes a generally circular base 2210 including a handle 2212 anda plurality of mounts 2220, 2230, and 2240 circumferentially spacedapart around the base 2210. Each of the mounts 2220, 2230, and 2240includes a generally cylindrical surface 2221, 2231, and 2241,respectively, defining a locking cover mounting tab receiving cavityconfigured to receive one of the locking cover mounting tabs of thestabilizers (described above). Additionally, each of the mounts 2220,2230, and 2240 includes an integrated latch strike to facilitate the useof the latches mounted to the stabilizers.

As best shown in FIGS. 24C and 24D, the underside of the locking cover2200 includes a surface 2211 b having a “inverted V-shaped”cross-section that defines a pre-filter securing channel around avertical axis through the center of the locking cover 2200. Thepre-filter 2900 is mounted to the locking cover by being press-fit intothe pre-filter mounting channel. The underside of the locking cover 2200also includes a plurality of generally flat annular surfaces 2211 d and2211 f that are connected by a downwardly-protruding sealing rib 2211 e(with respect to the orientation shown in FIGS. 24C and 24D).

In this example embodiment, the locking cover is a rotationally moldedplastic component. It should be appreciated, however, that the lockingcover may be made of any suitable material or materials or manufacturedin any suitable manner or manners.

2. Assembly

In this example embodiment, each fastener receiving opening of the lowerhousing component 2100 either: (a) is a threaded fastener receivingopening configured to receive a threaded fastener, or (b) includes anintegrated threaded insert (formed into the component or inserted afterthe component is formed) configured to receive a threaded fastener. Itshould be appreciated, however, that any suitable fastening mechanismsmay be employed to attach the components of the air filtration device toone another.

As best illustrated in FIG. 15, the fan assembly 2300 is attached to thefan assembly mounting bracket 3000 by: (a) inserting a portion of thebottom of the fan assembly 2300 through the fan assembly receivingopening 3040 of the fan assembly mounting bracket 3000, and (b)inserting fasteners through the fastener receiving openings 3040 of thefan assembly mounting bracket 3000 and threading those fasteners intofastener receiving openings of the fan assembly 2300.

As also best illustrated in FIG. 15, the motor capacitor 2320 isattached to the fan assembly mounting bracket 3000 by: (a) attaching oneend of the motor capacitor 2320 to the fan motor capacitor mountingbracket 3020, such as via any suitable fastener(s); (b) wrapping a fanmotor capacitor body securer 2325 around a portion of the body of thefan motor capacitor 2320; and (c) attaching the fan motor capacitor bodysecurer 2325 to the fan assembly mounting bracket 3000 via the fastenerreceiving opening 3032 using any suitable fastener(s). Although notshown, in this example embodiment, a fan speed sensor (described below)is attached to the fan speed sensor mounting bracket 3020 using anysuitable fastener(s).

As also best illustrated in FIG. 15, the fan assembly mounting bracket3000 is attached to the lower housing component 2100 within the fanassembly mounting chamber by inserting fasteners through the fastenerreceiving openings 3012 and threading those fasteners into correspondingfastener receiving openings of the fan assembly mounting bracketmounting surfaces 2117 a, 2117 b, and 2117 c of the interior sidesurface 2116 a of the base 2110.

The exhaust screen 2400 and the fan assembly mounting chamber cover 2500are attached to the base 2110 by: (a) positioning the exhaust screen2400 such that the flange 2453 is partially disposed within the exhaustscreen mounting channel 2153, the base mounting surface 2454 a abuts theexhaust screen mounting surface 2154 of the base 2110, and the basemounting surface 2455 a abuts the exhaust screen mounting surface 2155of the base 2110; (b) positioning the fan assembly mounting chambercover 2500 such that the exhaust screen mounting surface 2554 abuts thefan assembly mounting chamber cover mounting surface 2454 b of theexhaust screen 2400 and the exhaust screen mounting surface 2555 abutsthe fan assembly mounting chamber cover mounting surface 2455 b of theexhaust screen 2400; (c) inserting a fastener through the fastenerreceiving opening 2524 a of the fan assembly mounting chamber cover 2500and the fastener receiving opening 2456 of the exhaust screen 2400 andthreading that fastener into the fastener receiving opening 2154 a ofthe base 2110; (d) inserting a fastener through the fastener receivingopening 2524 b of the fan assembly mounting chamber cover 2500 and thefastener receiving opening 2457 of the exhaust screen 2400 and threadingthat fastener into the fastener receiving opening 2155 a of the base2110; and (e) inserting fasteners through the fastener receivingopenings 2514 of the fan assembly mounting chamber cover 2500 andthreading those fasteners into the corresponding fastener receivingopenings 2118 of the base 2110.

It should be appreciated that once the fan assembly mounting chambercover is attached to the base, the fan assembly mounting chamber coversubstantially covers the fan assembly mounting chamber and encloses thefan assembly and the fan assembly mounting bracket within the fanassembly mounting chamber. Additionally, once the fan assembly mountingchamber cover is mounted to the base, the exhaust port upper portion ofthe base and the exhaust port lower portion of the fan assembly mountingchamber cover form an exhaust port that defines an exhaust channel.

In this example embodiment, the exhaust port is substantially parallelto a plane extending between the stabilizers 2120 and 2130. This angleof the exhaust port improves fan efficiency by eliminating turbulenceand back pressure within the fan assembly mounting chamber. Further, thefact that the exhaust port is substantially parallel to a planeextending between the stabilizers 2120 and 2130 ensures that the airfiltration device will expel the filtered air substantially parallel tothe ground regardless of whether the air filtration device is operatingin an upright orientation or on its side (i.e., resting on thestabilizers 2120 and 2130).

The air director 3100 is attached to the base 2110 by: (a) positioningthe air director 3100 such that the air director mounting surfaces 3112b and 3114 b abut the first and second opposing sections 2115 b and 2115d, respectively, of the air director mounting surface 2115 of theexterior upper surface of the base 2110; (b) inserting a fastenerthrough the fastener receiving opening 3110 a of the air director 3100and threading that fastener into the fastener receiving opening 2114 aof the base 2110; and (c) inserting a fastener through the fastenerreceiving opening 3110 c of the air director 3100 and threading thatfastener into the fastener receiving opening 2114 c of the base 2110. Itshould be appreciated that the use of the air director to direct airdrawn through the filters into the fan assembly improves fan efficiency.

The HEPA filter securing bracket 2700 is mounted to the base 2110 by:(a) positioning the first and second HEPA filter securing bracketmounting tabs 2740 and 2750 atop the HEPA filter mounting bracketmounting surfaces 3112 a and 3114 a, respectively, of the air director3100; (b) inserting a fastener through the fastener receiving opening2740 a of the HEPA filter mounting bracket and through the fastenerreceiving opening 3110 b of the air director 3100 and threading thatfastener into the fastener receiving opening 2114 b of the base 2110;and (c) inserting a fastener through the fastener receiving opening 2750a of the HEPA filter mounting bracket and the fastener receiving opening3110 d of the air director 3100 and threading that fastener into thefastener receiving opening 2114 d of the base 2110.

To install the HEPA filter 2600, the HEPA filter 2600 is positionedaround the HEPA filter securing bracket 2700 and onto the base 2110 suchthat the lower end cap 2630 of the HEPA filter 2600 rests within theHEPA filter mounting channel. More specifically, as illustrated in FIG.22, the HEPA filter 2600 is positioned such that the mounting surface2630 c of the lower end cap 2630 rests atop securing rib 2111 e of theexterior upper surface of the base 2110.

The HEPA filter securing plate 2800 is then attached to the HEPA filtersecuring bracket 2700 by: (a) nesting the second annular bridgingportion 2840 and the third annular portion 2850 of the HEPA filtersecuring plate 2800 within the HEPA filter securing plate nestingsurface 2712 of the brace 2710 of the HEPA filter securing bracket 2700;and (b) inserting a fastener through the fastener receiving opening 2850a of the HEPA filter securing plate 2800 and threading that fastenerinto the fastener receiving opening 2715 a of the nut 2715 of the HEPAfilter securing bracket 2700.

As best shown in FIGS. 12H and 22, after the HEPA filter securing plate2800 is attached to the HEPA filter securing bracket 2700, the HEPAfilter 2600 is sandwiched between the HEPA filter securing plate 2800and the base 2110, thus ensuring that the HEPA filter 2600 will notdisengage from the base 2110 until the HEPA filter securing plate 2800is removed. Further, mounting the HEPA filter securing plate 2800 to theHEPA filter securing bracket 2700 causes the material of the lower endcap 2630 proximate the mounting surface 2630 c to compress around thesecuring rib 2111 e, which creates an airtight seal between the lowerend cap 2630 of the HEPA filter 2600 and the base 2110.

The pre-filter 2900 is installed by aligning the pre-filter limit switchactuator 2990 with the pre-filter limit switch actuator receivingopening 2175 of the base 2110 and press-fitting the pre-filter 2900downward into the pre-filter securing channel of the base 2110 until thepre-filter limit switch actuator 2990 actuates the pre-filter limitswitch.

The locking cover 2220 is attached to the lower housing component 2100by: (a) positioning the locking cover 2200 atop the stabilizers suchthat the locking cover mounting tab receiving opening defined by thesurface 2221 of the mount 2220 receives the locking cover mounting tab2121 of the stabilizer 2120, the locking cover mounting tab receivingopening defined by the surface 2231 of the mount 2230 receives thelocking cover mounting tab 2131 of the stabilizer 2130, and the lockingcover mounting tab receiving opening defined by the surface 2241 of themount 2240 receives the locking cover mounting tab 2141 of thestabilizer 2140; and (b) securing the latches attached to thestabilizers to their respective latch strikes of the locking cover 2200.Once the locking cover is attached to the lower housing component, theuser may carry or otherwise transport the air filtration device via thehandle 2212.

As best shown in FIG. 24D, attaching the locking cover 2200 to the lowerhousing component 2100 causes: (a) the upper edges 2912 and 2932 of thepre-filter 2900 to be press-fit into the pre-filter securing channel ofthe locking cover 2200, which secures the pre-filter 2900 in place; and(b) the material of the upper end cap 2620 of the HEPA filter proximatethe mounting surface 2620 c to compress around the securing rib 2211 eof the locking cover 2200, which creates an airtight seal between theupper end cap 2620 of the HEPA filter 2600 and the locking cover 2200.

In another embodiment, the locking cover is attached to one of thestabilizers of the lower housing component via a hinge. Thus, in thisembodiment, the locking cover is not completely detachable from thelower housing component. Rather, to remove the filters in thisembodiment, the latches are unlocked and the locking cover is rotatedvia the hinge off of the lower housing component to provide access tothe filters. In other embodiments, the locking cover attaches to thestabilizers in any suitable manner, such as through the use of threadedfasteners.

In this example embodiment, to replace the pre-filter the user detachesthe locking cover from the lower housing component, removes the oldpre-filter, and installs a new pre-filter as described above, andattaches the locking cover to the lower housing component. To replacethe HEPA filter, the user detaches the locking cover from the lowerhousing component, detaches the HEPA filter securing plate from the HEPAfilter securing bracket, removes the old HEPA filter, installs a newHEPA filter as described above, attaches the HEPA filter securing plateto the HEPA filter securing bracket, and attaches the locking cover tothe lower housing component. It should be appreciated that, in thisexample embodiment, the pre-filter and the HEPA filter are separatelyreplaceable.

It should be appreciated that the geometry of the base, the lockingcover, and the HEPA filter end caps that enable airtight sealing whenthe HEPA filter is installed eliminates need to include an additionalgasket to ensure proper sealing. It should also be appreciated that thegeometry of the pre-filter securing channels provides improved sealingwhen the pre-filter is installed. It should further be appreciated thatthe fact that: (a) the pre-filter securing channel of the lower housingcomponent is lower relative to the HEPA filter mounting channel of thelower housing component, and (b) the pre-filter securing channel of thelocking cover is higher than the HEPA filter mounting channel of thelocking cover improves the accuracy of the measurements taken by thepressure sensors.

3. Electronics

FIG. 25 is a block diagram showing certain electronic components of thisexample embodiment of the air filtration device of the presentdisclosure. In this example embodiment, the air filtration device 2010includes: (a) a controller 3650; (b) the fan 2310 of the fan assembly2300; (c) at least one sound producing device 3850; (d) a control panel2160 including or otherwise associated with: (i) an operating modeselector 2161, (ii) a pre-filter fault indicator 2162, (iii) a pluralityof pre-filter status indicators 2163, (iv) a HEPA filter fault indicator2164, (v) a plurality of HEPA filter status indicators 2165, (vi) an airfiltration device status indicator 2166, and (vii) an hour meter display2167; and (e) a plurality of sensors including: (i) a dust sensor 3910,(ii) a pre-filter differential pressure sensor 3920, (iii) a HEPA filterdifferential pressure sensor 3930, (iv) a fan differential pressuresensor 3940, (v) a fan speed sensor 3950, and (vi) a pre-filter presencesensor 3960. It should be appreciated that the air filtration device2010 and each of the above-listed electronic components are powered by apower source, such as an A/C power source 20.

In this example embodiment, the controller 3650: (1) communicates witheach of the other electronic components, (2) receives communicationsfrom each of the other electronic components, and (3) controls each ofthe other electronic components. The controller may be any suitableprocessing device or set of processing devices, such as amicroprocessor, a microcontroller-based platform, a suitable integratedcircuit, one or more application-specific integrated circuits (ASICs),or any other suitable circuit boards.

In certain embodiments, the controller of the air filtration device isconfigured to communicate with, configured to access, and configured toexchange signals with the at least one memory device or data storagedevice. In various embodiments, the at least one memory device includesrandom access memory (RAM), which can include non-volatile RAM (NVRAM),magnetic RAM (MRAM), ferroelectric RAM (FeRAM), and other suitable formsof RAM. In other embodiments, the at least one memory device includesread only memory (ROM). In certain embodiments, the at least one memorydevice includes flash memory and/or electrically erasable programmableread only memory (EEPROM). It should be appreciated that the at leastone memory device may include any other suitable magnetic, optical,and/or semiconductor memory.

As generally described below, in various embodiments, the at least onememory device of the air filtration device stores program code andinstructions executable by the controller of the air filtration deviceto control various processes performed by the air filtration device. Theat least one memory device also stores other operating data, such asimage data, event data, and/or input data. In various embodiments, partor all of the program code and/or the operating data described above isstored in at least one detachable or removable memory device including,but not limited to, a cartridge, a disk, a CD-ROM, a DVD, a USB memorydevice, or any other suitable non-transitory computer readable medium.In certain such embodiments, a user uses such a removable memory deviceto implement at least part of the present disclosure. In otherembodiments, part or all of the program code and/or the operating datais downloaded to the at least one memory device of the air filtrationdevice through any suitable data network (such as an internet, anintranet, or a cellular communications network).

In this example embodiment, the fan assembly 2300 is a RadiCalR2E250-RB02-15 centrifugal fan, though it should be appreciated that anyother suitable fan assembly may be employed.

In this example embodiment, the sound producing device 3850 is a MallorySonalert Products Inc. PB-1224PE-05Q sound producing device, though itshould be appreciated that any suitable sound producing device may beemployed. In this example embodiment, as described in detail below, theair filtration device uses the sound producing device 3850 to output thefollowing audible tones: (a) a major air filtration device malfunctiontone when the air filtration device determines that a major airfiltration device malfunction occurs (described below), (b) a filterchange alarm tone when the air filtration device determines that thepre-filter occlusion level exceeds the pre-filter shutdown threshold andneeds replacement and/or when the HEPA filter occlusion level exceedsthe HEPA filter shutdown threshold and needs replacement (as describedbelow), and (c) a filter fault indicator tone when the air filtrationdevice determines that an acceptable pre-filter is not installed and/oran acceptable HEPA filter is not installed (as described below).

In this example embodiment, the major air filtration device malfunctiontone, the filter change alarm tone, and the filter fault tone aredifferent. More specifically: (a) the major air filtration devicemalfunction tone includes a continuous tone; (b) the filter change alarmtone includes a one tone combination (beep-pause, beep-pause); and (c)the filter fault tone includes a two tone combination (beep-beep-pause,beep-beep-pause). In this example embodiment, setting the air filtrationdevice to the standby operating mode or powering the air filtrationdevice off causes the controller to silence the sound producing device3850.

i. Control Panel

The operating mode selector 2161 enables the user to select theoperating mode in which the user desires the air filtration device tooperate. More specifically, in this example embodiment, the operatingmode selector 2161 enables the user to select one of the followingoperating modes: one of the manual fan speed setting operating modes,the automatic fan speed setting selection operating mode, or the standbyoperating mode, each of which are described below. In this exampleembodiment, the operating mode selector 2161 includes a control knobthat the user may rotate to indicate the desired operating mode.

In another embodiment, the operating mode selector includes a touchscreen display that enables the user to select the desired operatingmode by touching an appropriate area of the touch screen. The airfiltration device sets the operating mode to the desired operating modeafter receiving such input. In another embodiment, the operating modeselector includes a display and one or more associated buttons. In thisembodiment, the user selects an operating mode by using the one or morebuttons to select the desired operating mode. The air filtration devicesets the operating mode to the desired operating mode after receivingsuch input.

In another embodiment, the air filtration device enables the user to usea computing device, such as (but not limited to) a cellular phone, atablet computing device, a laptop computing device, and/or a desktopcomputing device, to select the desired operating mode. That is, in thisembodiment: (a) the computing device receives an input of the user'sdesired operating mode; (b) the computing device communicates the user'sdesired operating mode to the air filtration device, such as (but notlimited to) through a wireless network connection, a cellular networkconnection, a wired network connection, an infrared connection, or aBluetooth connection; and (c) the air filtration device receives thecommunication from the computing device and sets the operating mode tothe desired operating mode. It should be appreciated that, in thisembodiment, the air filtration device enables the user to remotelychange the operating mode of the air filtration device, such as fromacross the room or across the jobsite, which saves the time it wouldotherwise take the user to travel to the air filtration device to changethe operating mode (such as via the control knob).

In another embodiment, the air filtration device enables the user to usea remote control to select the desired operating mode. That is, in thisembodiment: (a) the remote control receives an input of the user'sdesired operating mode; (b) the remote control communicates the user'sdesired operating mode to the air filtration device, such as through anyof the above-listed connections; and (c) the air filtration devicereceives the communication from the remote control and sets theoperating mode to the desired operating mode. In one such embodiment,the remote control also displays one or more of the pre-filter faultindicator, the HEPA filter fault indicator, the air filtration devicestatus indicator, the pre-filter status indicators, and the HEPA filterstatus indicators.

The air filtration device employs the pre-filter fault indicator 2162 toindicate that there is a problem with the pre-filter. In this exampleembodiment, the pre-filter fault indicator 2162 includes a redlight-emitting diode (LED). As described in detail below, the airfiltration device lights the red LED of the pre-filter fault indicatorwhen any of: (a) an acceptable pre-filter is not installed; and (b) thepre-filter occlusion level exceeds the pre-filter shutdown threshold(i.e., when the pre-filter needs replacement). It should be appreciatedthat any suitable pre-filter fault indicator(s) may be employed inaddition to or instead of a red LED, such as (but not limited to): adifferent-colored LED, a light other than an LED, a display screen, aremote control display, a computing device, and/or a non-displayindicator such as an audible tone.

The air filtration device employs the pre-filter status indicators 2163to indicate the occlusion level of the pre-filter. In this exampleembodiment, the pre-filter status indicators 2163 include a green LED, ayellow LED, and a red LED. As described in detail below, the airfiltration device: (a) lights the green LED of the pre-filter statusindicators when the Clean pre-filter occlusion level range includes thedetermined pre-filter occlusion level; (b) lights the yellow LED of thepre-filter status indicators when the Slightly Occluded pre-filterocclusion level range includes the determined pre-filter occlusionlevel; (c) lights the red LED of the pre-filter status indicators whenthe Highly Occluded pre-filter occlusion level range includes thedetermined pre-filter occlusion level; and (d) lights the red LED of thepre-filter status indicators in a flashing or blinking manner when thepre-filter occlusion level range exceeds the pre-filter shutdownthreshold (i.e., when the pre-filter needs replacement). It should beappreciated that any suitable pre-filter status indicators may beemployed in addition to or instead of green, yellow, and red LEDs, suchas (but not limited to): a single LED that can display a plurality ofdifferent colors, different-colored LED, lights other than LEDs, one ormore display screens, a remote control display, a computing device,and/or a non-display indicator such as an audible tone.

The air filtration device employs the HEPA filter fault indicator 2164to indicate that there is a problem with the HEPA filter. In thisexample embodiment, the HEPA filter fault indicator 2164 includes a redLED. As described in detail below, the air filtration device lights thered LED of the HEPA filter fault indicator when any of: (a) anacceptable HEPA filter is not installed, and (b) the HEPA filterocclusion level exceeds the HEPA filter shutdown threshold (i.e., whenthe HEPA filter needs replacement). It should be appreciated that anysuitable HEPA filter fault indicator(s) may be employed in addition toor instead of a red LED, such as (but not limited to): adifferent-colored LED, a light other than an LED, a display screen, aremote control display, a computing device, and/or a non-displayindicator such as an audible tone.

The air filtration device employs the HEPA filter status indicators 2165to indicate the occlusion level of the HEPA filter. In this exampleembodiment, the HEPA filter status indicators 2165 include a green LED,a yellow LED, and a red LED. As described in detail below, the airfiltration device: (a) lights the green LED of the HEPA filter statusindicators when the Clean HEPA filter occlusion level range includes thedetermined HEPA filter occlusion level; (b) lights the yellow LED of theHEPA filter status indicators when the Slightly Occluded HEPA filterocclusion level range includes the determined HEPA filter occlusionlevel; (c) lights the red LED of the HEPA filter status indicators whenthe Highly Occluded HEPA filter occlusion level range includes thedetermined HEPA filter occlusion level; and (d) lights the red LED ofthe HEPA filter status indicators in a flashing or blinking manner whenthe HEPA filter occlusion level range exceeds the HEPA filter shutdownthreshold (i.e., when the HEPA filter needs replacement). It should beappreciated that any suitable HEPA filter status indicators may beemployed in addition to or instead of green, yellow, and red LEDs, suchas (but not limited to): a single LED that can display a plurality ofdifferent colors, different-colored LED, lights other than LEDs, one ormore display screens, a remote control display, a computing device,and/or a non-display indicator such as an audible tone.

The air filtration device employs the air filtration device statusindicator 2166 to indicate that the air filtration device is operatingnormally or to indicate that there is a problem with the air filtrationdevice. In this example embodiment, the air filtration device statusindicator 2166 includes an LED that can display a green or red light. Asdescribed in detail below, the air filtration device: (a) lights the LEDof the air filtration device status indicator green when the airfiltration device is operating in any of the manual fan speed settingoperating modes, the automatic fan speed setting selection operatingmode, or the standby operating mode; and (b) lights the LED of the airfiltration device status indicator red when any of: (i) an acceptablepre-filter is not installed; (ii) an acceptable HEPA filter is notinstalled; (iii) the air filtration device is in shutdown mode and theautomatic fan speed setting selection operating mode or the manualmaximum fan speed setting operating mode is selected; (iv) the airfiltration device is in shutdown mode, the manual medium fan speedsetting operating mode or the manual minimum fan speed setting operatingmode is selected, and the designated shutdown time period has expired;and (v) a major air filtration device malfunction occurs. In thisexample embodiment, whenever the air filtration device lights the LED ofthe air filtration device status indicator red, the power switch must becycled “OFF” and back “ON” to clear the fault. In certain embodiments,when the air filtration device is in shutdown mode and the automatic fanspeed setting selection operating mode or the manual maximum fan speedsetting operating mode is selected such that the air filtration devicelights the LED of the air filtration device status indicator red, theair filtration device clears the fault when the standby operating mode,the manual medium fan speed setting operating mode, or the manualminimum fan speed setting operating mode is selected.

It should be appreciated that any suitable air filtration device statusindicators may be employed in addition to or instead of an LED, such as(but not limited to): different-colored LED, lights other than LEDs, aplurality of LEDs, one or more display screens, a remote controldisplay, and/or a computing device.

The air filtration device tracks or counts the number of hours the fanis operating at any fan speed and displays that number of hours on thehour meter display 2167. In this example embodiment, the hour meterdisplay 2167 includes a six digit LED display. Additionally, in thisexample embodiment, the air filtration device does not enable a user toreset the hour count; the air filtration device retains the hour countwhen the power is disconnected (e.g., when the air filtration device isunplugged); and the air filtration device can roll over the hour counteronce the hour meter display reaches a maximum displayed number of hours(such as 99999.9 hours for a six-digit hour meter display including onedecimal place). It should be appreciated that the hour meter display maybe any suitable indicator other than or in addition to a six-digit LEDdisplay.

In certain embodiments, the air filtration device communicates with acomputing device of the user, such as (but not limited to) a cellularphone, a tablet computing device, a laptop computing device, and/or adesktop computing device, and causes the computing device to displaycertain information, such as one or more of: the pre-filter faultindicator, the HEPA filter fault indicator, the air filtration devicestatus indicator, the pre-filter status indicators, the HEPA filterstatus indicators, and the selected operating mode. For instance, in oneexample, the user executes an application on the user's smartphone thatsyncs and communicates with the air filtration device. The user may thenuse the application to monitor the status of the air filtration device(such as by viewing one or more of the pre-filter fault indicator, theHEPA filter fault indicator, the air filtration device status indicator,the pre-filter status indicators, the HEPA filter status indicators, andthe selected operating mode) remotely, such as from across the room oracross the jobsite. Additionally, as described above, in certainembodiments the computing device of the user enables the user to inputinstructions to control certain aspects of the air filtration device andcommunicates such instructions to the air filtration device.

ii. Sensors

The dust sensor 3910 determines the level of dust or impurities in theair surrounding the air filtration device. In this example embodiment,the dust sensor includes an optical dust sensor, such as a SharpGP2Y1010AU0F optical dust sensor, though it should be appreciated thatany suitable sensor may be employed to detect the level of dust in theair.

The pre-filter differential pressure sensor 3920 measures thedifferential pressure across the pre-filter. More specifically, thepre-filter differential pressure sensor includes two ports: (1) a firstopen port; and (2) a second port connected to the pressure sensor port2170 b located between the pre-filter and the HEPA filter (i.e., locateddownstream of the pre-filter and upstream of the HEPA filter). Thepre-filter differential pressure sensor determines the differentialpressure across the pre-filter by measuring the pressures at the firstand second ports and determining the difference between those pressuremeasurements.

The HEPA filter differential pressure sensor 3930 measures thedifferential pressure across the HEPA filter. More specifically, theHEPA filter differential pressure sensor includes two ports: (1) a firstport connected to the pressure sensor port 2170 b located between thepre-filter and the HEPA filter (i.e., located downstream of thepre-filter and upstream of the HEPA filter); and (2) a second portconnected to the pressure sensor port 2170 a located between the HEPAfilter and the fan assembly (i.e., located downstream of the HEPA filterand upstream of the fan assembly). The HEPA filter differential pressuresensor determines the differential pressure across the HEPA filter bymeasuring the pressures at the first and second ports and determiningthe difference between those pressure measurements.

The fan differential pressure sensor 3940 measures the differentialpressure across the fan. More specifically, the fan differentialpressure sensor includes two ports: (1) a first port connected to thepressure sensor port 2170 a located between the HEPA filter and the fanassembly (i.e., located downstream of the HEPA filter and upstream ofthe fan assembly); and (2) a second port connected to the pressuresensor port 2119 located downstream of the fan assembly. The fandifferential pressure sensor determines the differential pressure acrossthe fan by measuring the pressures at the first and second ports anddetermining the difference between those pressure measurements.

In this embodiment, the differential pressure sensors are Freescale+/−1.45 PSI MPXV7002DP differential pressure sensors, though it shouldbe appreciated that any suitable differential pressure sensors may beemployed.

In other embodiments, rather than employing three differential pressuresensors, the air filtration device includes absolute pressure sensorsand determines the appropriate differential pressures using measuredabsolute pressures. For instance, in one example embodiment, the airfiltration device includes: (a) a first absolute pressure sensorincluding an open port, (b) a second absolute pressure sensor includinga port connected to the pressure sensor port located between thepre-filter and the HEPA filter, (c) a third absolute pressure sensorincluding a port connected to the pressure sensor port located betweenthe HEPA filter and the fan assembly, and (d) a fourth absolute pressuresensor including a port connected to the pressure sensor port locateddownstream of the fan assembly. In this example embodiment, the airfiltration device: (a) determines the differential pressure across thepre-filter by determining the difference between the pressuremeasurements of the first and second absolute pressure sensors, (b)determines the differential pressure across the HEPA filter bydetermining the difference between the pressure measurements of thesecond and third absolute pressure sensors, and (c) determines thedifferential pressure across the fan by determining the differencebetween the pressure measurements of the third and fourth absolutepressure sensors.

The fan speed sensor 3950 measures the speed of the fan 2310, such asthe number of revolutions per minute at which the fan 2310 is spinning.In this example embodiment, the fan speed sensor includes an optical fanspeed sensor, such as an Optek OPB716Z sensor, though it should beappreciated that any suitable fan speed sensor may be employed. Inanother embodiment, the fan assembly includes an integrated fan speedsensor and communicates the fan speed to the controller. In thisembodiment, the air filtration device does not include a separate fanspeed sensor in addition to the integrated fan speed sensor of the fanassembly.

The pre-filter presence sensor 3960 determines whether an acceptablepre-filter is installed in the air filtration device, as described belowwith respect to the pre-filter presence detection process 6000. In thisexample embodiment, the lower housing component supports or otherwiseincludes a pre-filter presence sensor in the form of a pre-filter limitswitch that is actuatable by the pre-filter limit switch actuator of thepre-filter. In another embodiment, the pre-filter presence sensor is aHall Effect sensor that detects a metallic element included in thepre-filter, as described below. In another embodiment, the pre-filterpresence sensor is a radio frequency identification (RFID) readerconfigured to read or recognize an RFID tag included in the pre-filter,as described below. It should be appreciated that any other suitablepre-filter presence sensor may be employed.

4. Operations

It should be appreciated that the below-described operations andprocesses may be performed regardless of the shapes of the filters. Forinstance, the below-described operations and processes may be performedin an air filtration device employing two substantially flat filters orsemicircular filters positioned one in front of the other.

a. Power-Up Process

In this example embodiment, as noted above, the air filtration deviceincludes a power switch 2176 that powers the air filtration device onand off when the air filtration device is connected to a power source(such as an A/C power source). When the air filtration device isconnected to a power source and the air filtration device is powered on(i.e., the power switch is switched to “ON”), the air filtration device:(a) displays “CAL” on the hour meter display; (b) lights the LED of theair filtration device status indicator green; (c) lights the green LEDof the pre-filter status indicators in a flashing manner; (d) lights thegreen LED of the HEPA filter status indicators in a flashing manner; and(e) after waiting (if necessary) for the fan speed to fall below 100revolutions per minute, calibrates the pre-filter differential pressuresensor, the HEPA filter differential pressure sensor, and the fandifferential pressure sensor by taking and averaging several pressuremeasurements.

After calibrating the differential pressure sensors: (a) if the standbyoperating mode is selected, the air filtration device enters fullstandby mode (described below); and (b) if the automatic fan speedsetting selection operating mode or any of the manual fan speed settingoperating modes is selected, the air filtration device enters thatselected (non-standby) operating mode.

It should be appreciated that this is one example of the power-upprocess. In other embodiments, the power-up process may includedifferent or additional steps and/or may not include certain of theabove-described steps.

b. Fan Speed Settings

In this example embodiment, the air filtration device is operable at anyof a plurality of different fan speed settings including at least aminimum fan speed setting and a maximum fan speed setting. Each fanspeed setting corresponds to a different desired air flow rate throughthe air filtration device. For instance, in this example embodiment, theair filtration device is operable at any of three fan speed settingsincluding: (a) a minimum fan speed setting that corresponds to a firstdesired air flow rate through the air filtration device, (b) a mediumfan speed setting that corresponds to a second desired air flow ratethrough the air filtration device, and (c) a maximum fan speed settingthat corresponds to a third desired rate of air flow through the airfiltration device. In this example embodiment, the third desired airflow rate through the air filtration device is 600 cubic feet perminute, which is greater than the second desired air flow rate throughthe air filtration device, which is 400 cubic feet per minute, which isgreater than the first desired air flow rate through the air filtrationdevice, which is 200 cubic feet per minute.

It should be appreciated that, in other embodiments, the air filtrationdevice may be operable at any suitable number of different fan speedsettings. It should also be appreciated that the particular air flowrates associated with the different fan speed settings may be anysuitable air flow rates.

It should also be appreciated that “current fan speed setting” as usedherein refers to the fan speed setting at which the air filtrationdevice is operating at a particular point in time. For instance: (a) ata particular point in time, if one of the manual fan speed settingoperating modes (described below) is selected, the current fan speedsetting (i.e., the fan speed setting at that particular point in time)is the fan speed setting associated with that selected manual fan speedsetting operating mode; and (b) at a particular point in time, if theautomatic fan speed setting selection operating mode (described below)is selected, the current fan speed setting (i.e., the fan speed settingat that particular point in time) is the fan speed setting selected bythe air filtration device via the automatic fan speed setting selectionprocess (described below).

c. Operating Modes

In this example embodiment, the air filtration device includes aplurality of different user-selectable operating modes including aplurality of different manual fan speed setting operating modes, anautomatic fan speed setting selection operating mode, and a standbyoperating mode. As described above, the operating modes are selectableusing the operating mode selector.

i. Manual Fan Speed Setting Operating Modes

In this example embodiment, the air filtration device includes adifferent user-selectable manual fan speed setting operating modecorresponding to each fan speed setting at which the air filtrationdevice may operate. This enables the user to manually select and set thefan speed setting at which the user desires the air filtration device tooperate.

In this example embodiment, the air filtration device includes: (a) auser-selectable manual minimum fan speed setting operating mode that,when selected by the user, sets the fan speed setting to the minimum fanspeed setting (which corresponds to the first desired air flow ratethrough the air filtration device) and causes the air filtration deviceto operate at the minimum fan speed setting; (b) a user-selectablemanual medium fan speed setting operating mode that, when selected bythe user, sets the fan speed setting to the medium fan speed setting(which corresponds to the second desired air flow rate through the airfiltration device) and causes the air filtration device to operate atthe medium fan speed setting; and (c) a user-selectable manual maximumfan speed setting operating mode that, when selected by the user, setsthe fan speed setting to the maximum fan speed setting (whichcorresponds to the third desired air flow rate through the airfiltration device) and causes the air filtration device to operate atthe maximum fan speed setting.

In this example embodiment, when the air filtration device is operatingin either the manual maximum fan speed setting operating mode or themanual medium fan speed setting operating mode such that the fan speedsetting is either the maximum fan speed setting or the medium fan speedsetting, the air filtration device employs dynamic fan speed control toadjust the fan speed to achieve the desired air flow rate through theair filtration device. Dynamic fan speed control is described in detailbelow.

On the other hand, in this example embodiment, when the air filtrationdevice is operating in the manual minimum fan speed setting operatingmode such that the fan speed setting is the minimum fan speed setting,the air filtration device operates the fan at a substantially constant,designated fan speed. In other words, when the air filtration device isoperating in the manual minimum fan speed setting operating mode suchthat the fan speed setting is the minimum fan speed setting, the airfiltration device does not employ dynamic fan speed control in thisexample embodiment. It should be appreciated, however, that in otherembodiments the air filtration device employs dynamic fan speed controlwhen the fan speed setting is the minimum fan speed setting.

In other embodiments, the air filtration device does not include amanual fan speed setting operating mode associated with each fan speedsetting at which the air filtration device may operate. For instance, inone example embodiment in which the air filtration device includes fivefan speed settings at which the air filtration device may operate, theair filtration device includes manual fan speed setting operating modesassociated with a first, third, and fifth fan speed setting and does notinclude a manual fan speed setting operating mode associated with asecond and fourth fan speed setting. In another embodiment, the airfiltration device does not include any manual fan speed settingoperating modes. In another embodiment, the air filtration deviceincludes a single manual fan speed setting operating mode.

ii. Automatic Fan Speed Setting Selection Operating Mode

In this example embodiment, the air filtration device includes auser-selectable automatic fan speed setting selection operating mode.Generally, when the automatic fan speed setting selection operating modeis selected by the user, the air filtration device uses the dust sensorto measure the amount of dust in the air surrounding the air filtrationdevice and, if necessary, automatically increases or decreases the fanspeed setting to account for the amount of dust in the air. Thus, whenoperating in the automatic fan speed setting selection operating mode,the air filtration device dynamically and automatically adjusts the fanspeed setting in real-time to account for varying levels of dust in theair surrounding the air filtration device, which eliminates the need forthe user to guess the amount of dust in the air and manually select whatthe user believes to be the most effective and efficient fan speedsetting in which to operate the air filtration device to remove thatdust.

More specifically, in this example embodiment, each of the fan speedsettings is associated with a different range of dust levels. The rangeof dust levels associated with a particular fan speed setting includesthe dust levels that the air filtration device may most effectively andefficiently manage or clean when operating at that particular fan speedsetting. For instance, in this example embodiment: (a) the minimum fanspeed setting is associated with a first range of dust levels beginningat zero and ending at a maximum dust level associated with the minimumfan speed setting; (b) the medium fan speed setting is associated with asecond range of dust levels beginning at a minimum dust level associatedwith the medium fan speed setting, which is greater than the maximumdust level associated with the minimum fan speed setting, and ending ata maximum dust level associated with the medium fan speed setting; and(c) the maximum fan speed setting is associated with a third range ofdust levels beginning at a minimum dust level associated with themaximum fan speed setting, which is greater than the maximum dust levelassociated with the medium fan speed setting, and ending at a maximummeasurable dust level, which is the highest dust level measurable by thedust sensor.

For instance, Table 1 below includes example ranges of dust levelsassociated with the minimum, medium, and maximum fan speed settings. Inthis example, the dust levels range from zero to ten. It should beappreciated that each fan speed setting may be associated with anysuitable range of dust levels, and that each range of dust levels mayinclude any suitable dust levels.

TABLE 1 Example Ranges of Dust Levels Associated With Example Fan SpeedSettings Fan Speed Setting Range of Dust Levels Minimum 0 to 3 Medium 4to 6 Maximum 7 to 10

Thus, in this example: (a) when the measured dust level is 0, 1, 2, or3, the air filtration device most effectively and efficiently manages orcleans the dust when operating at the minimum fan speed setting; (b)when the measured dust level is 4, 5, or 6, the air filtration devicemost effectively and efficiently manages or cleans the dust whenoperating at the medium fan speed setting; and (c) when the measureddust level is 7, 8, 9, or 10, the air filtration device most effectivelyand efficiently manages or cleans the dust when operating at the maximumfan speed setting.

At each of a plurality of predetermined dust level sensing timeintervals, such as every fifteen seconds (or any other suitable lengthof time), the air filtration device measures the dust level using thedust level sensor and determines whether the range of dust levelsassociated with the current fan speed setting includes the measured dustlevel. If the range of dust levels associated with the current fan speedsetting includes the measured dust level, the air filtration devicemaintains the current fan speed setting. If the measured dust levelexceeds the range of dust levels associated with the current fan speedsetting, the air filtration device increases the fan speed setting. Ifthe measured dust level falls below the range of dust levels associatedwith the current fan speed setting for a designated number ofconsecutive dust level sensing time intervals, the air filtration devicedecreases the fan speed setting.

FIG. 26 illustrates a flowchart of one example embodiment of anautomatic fan speed setting selection process or method 4000 of thepresent disclosure. In various embodiments, the automatic fan speedsetting selection process 4000 is represented by a set of instructionsstored in one or more memories and executed by the controller. Althoughthe automatic fan speed setting selection process 4000 is described withreference to the flowchart shown in FIG. 26, it should be appreciatedthat many other processes of performing the acts associated with thisillustrated automatic fan speed setting selection process may beemployed. For example, the order of certain of the illustrated blocksand/or diamonds may be changed, certain of the illustrated blocks and/ordiamonds may be optional, and/or certain of the illustrated blocksand/or diamonds may not be employed.

The automatic fan speed setting selection process 4000 starts when theair filtration device receives a selection of the automatic fan speedsetting selection operating mode. The air filtration device sets the fanspeed setting to the minimum fan speed setting such that the current fanspeed setting is the minimum fan speed setting, as indicated by block4100. As explained above, each fan speed setting is associated with adifferent range of dust levels including a minimum dust level and amaximum dust level. The air filtration device sets the variable n equalto zero, as indicated by block 4110. The variable n represents a numberof dust level sensing time intervals in which the measured dust levelduring that particular dust level sensing time interval is less than theminimum dust level in the range of dust levels associated with thecurrent fan speed setting during that particular dust level sensing timeinterval. The air filtration device measures the dust level using thedust sensor, as indicated by block 4120.

The air filtration device determines if the measured dust level isgreater than the maximum dust level in the range of dust levelsassociated with the current fan speed setting, as indicated by diamond4130. If the air filtration device determines that the measured dustlevel is greater than the maximum dust level in the range of dust levelsassociated with the current fan speed setting, the air filtration deviceincreases the fan speed setting, such as by one level (e.g., from theminimum fan speed setting to the medium fan speed setting or from themedium fan speed setting to the maximum fan speed setting), as indicatedby block 4140. The air filtration device determines whether a dust levelsensing time interval has elapsed, as indicated by diamond 4150. If theair filtration device determines that the dust level sensing timeinterval has elapsed, the process 4000 returns to the block 4120. If, onthe other hand, the air filtration device determines that the dust levelsensing time interval has not elapsed, the air filtration devicemaintains the current fan speed setting, as indicated by block 4160, andthe process 4000 returns to the diamond 4150.

Returning to the diamond 4130, if the air filtration device determinesthat the measured dust level is not greater than the maximum dust levelin the range of dust levels associated with the current fan speedsetting, the air filtration device determines if the measured dust levelis less than the minimum dust level in the range of dust levelsassociated with the current fan speed setting, as indicated by diamond4170. If the air filtration device determines that the measured dustlevel is not less than the minimum dust level in the range of dustlevels associated with the current fan speed setting, the air filtrationdevice sets the variable n equal to zero, and the process 4000 proceedsto the block 4160, described above.

If, on the other hand, the air filtration device determines that themeasured dust level is less than the minimum dust level in the range ofdust levels associated with the current fan speed setting, the airfiltration device sets the variable n equal to n+1, as indicated byblock 4190. The air filtration device determines if the variable n is atleast equal to a designated number, as indicated by diamond 4200. If theair filtration device determines that the variable n is not at leastequal to the designated number, the process 4000 proceeds to the block4160. If, on the other hand, the air filtration device determines thatthe variable n is at least equal to the designated number, the airfiltration device decreases the fan speed setting, such as by one level(e.g., from the maximum fan speed setting to the medium fan speedsetting or from the medium fan speed setting to the minimum fan speedsetting), as indicated by block 4220. The air filtration device sets thevariable n equal to zero, and the process 4000 proceeds to the diamond4150.

In this example embodiment, the designated number is four such that theair filtration device decreases the fan speed setting when the airfiltration device determines that the measured dust level is less thanthe minimum dust level in the range of dust levels associated with thecurrent fan speed setting for four consecutive dust level sensing timeintervals. It should be appreciated, however, that the designated numbermay be any suitable number in other embodiments. It should also beappreciated that, in certain embodiments, the designated number is equalto one. Thus, in these embodiments, the air filtration device decreasesthe fan speed setting when the air filtration device determines that themeasured dust level is less than the minimum dust level in the range ofdust levels associated with the current fan speed setting.

In the example embodiment described above with respect to FIG. 26, theair filtration device increases or decreases the fan speed setting onelevel at a time. In other embodiments, however, the air filtrationdevice may increase or decrease the fan speed level a plurality oflevels at a time. For instance, in one example embodiment, if themeasured dust level is not within the range of dust levels associatedwith the current fan speed setting, the air filtration device switchesthe fan speed setting to the fan speed setting associated with the rangeof dust levels that includes the measured dust level. For instance, ifthe current fan speed setting is the minimum fan speed setting and themeasured dust level is included in the range of dust levels associatedwith the maximum fan speed setting, the air filtration device changesthe fan speed setting to the maximum fan speed setting (bypassing themedium fan speed setting). Alternatively, if the current fan speedsetting is the maximum fan speed setting and the measured dust level isincluded in the range of dust levels associated with the minimum fanspeed setting for a designated number of consecutive dust level sensingtime intervals, the air filtration device changes the fan speed settingto the minimum fan speed setting (bypassing the medium fan speedsetting).

In other embodiments, when operating in the automatic fan speed settingselection operating mode, the air filtration device powers the fan offwhen the measured dust level is a designated dust level or within adesignated range of dust levels. For instance, Table 2 below includesexample ranges of dust levels associated with the off, minimum, medium,and maximum fan speed settings. In this example, the dust levels rangefrom zero to ten. It should be appreciated that each fan speed settingmay be associated with any suitable range of dust levels, and that eachrange of dust levels may include any suitable dust levels.

TABLE 2 Example Ranges of Dust Levels Associated With Example Fan SpeedSettings Fan Speed Setting Range of Dust Levels Off 0 Minimum 1 to 3Medium 4 to 6 Maximum 7 to 10

Thus, in this example: (a) when the measured dust level is 0, the airfiltration device powers the fan off because filtration is not required;(b) when the measured dust level is 1, 2, or 3, the air filtrationdevice most effectively and efficiently manages or cleans the dust whenoperating at the minimum fan speed setting; (c) when the measured dustlevel is 4, 5, or 6, the air filtration device most effectively andefficiently manages or cleans the dust when operating at the medium fanspeed setting; and (d) when the measured dust level is 7, 8, 9, or 10,the air filtration device most effectively and efficiently manages orcleans the dust when operating at the maximum fan speed setting. Thus,in this example embodiment, when operating in the automatic fan speedsetting selection operating mode, the air filtration device onlyoperates fan when the measured dust level is greater than zero (thoughit should be appreciated that the threshold minimum dust level thatcauses operation of the fan may be any suitable dust level).

iii. Standby Operating Mode

In this example embodiment, the air filtration device includes auser-selectable standby operating mode in which the air filtrationdevice is powered on but in which the fan does not operate. If the airfiltration device receives a selection of the standby operating modeupon power-up of the air filtration device, the air filtration devicelights the LED of the air filtration device status indicator green. Ifthe standby operating mode is selected after the air filtration devicehas determined the occlusion levels of the filters (described below) andhas indicated such occlusion levels by lighting the appropriatepre-filter and HEPA filter status indicators, the air filtration devicemaintains those filter occlusion level indicators for a designatedperiod, such as 10 seconds (or any other suitable period of time). Oncethe designated period expires, the air filtration device enters fullstandby operating mode. Once in full standby operating mode, when theautomatic fan speed setting selection operating mode or any of themanual fan speed setting operating modes is selected, the air filtrationdevice performs the filter occlusion level monitoring process (describedbelow).

d. Dynamic Fan Speed Control

As noted above, in certain instances, the air filtration device employsdynamic fan speed control to adjust the fan speed to achieve a desiredair flow rate through the air filtration device. Generally, whenemploying dynamic fan speed control, the air filtration device uses thedifferential pressure across the fan and the desired air flow ratethrough the air filtration device to determine a desired fan speed thatachieves the desired flow rate through the air filtration device. Thisenables the air filtration device to maintain that desired air flow ratethrough the air filtration device by varying the fan speed as thepre-filter and the HEPA filter occlude during operation of the airfiltration device, which prevents the air flow rate through the airfiltration device from falling below the desired air flow rate andimpairing the air filtration device's performance.

In this example embodiment, the air filtration device employs dynamicfan speed control when the current fan speed setting is one of at leastone designated fan speed setting. Here, the maximum fan speed settingand the medium fan speed setting are designated fan speed settings and,therefore, the air filtration device employs dynamic fan speed controlwhen the air filtration device is operating at either of these fan speedsettings. The minimum fan speed setting is not a designated fan speedsetting in this example embodiment and, therefore, the air filtrationdevice does not employ dynamic fan speed control when the air filtrationdevice is operating at the minimum fan speed setting. It should beappreciated that, in other embodiments: (a) all of the fan speedsettings are designated fan speed settings; (b) a plurality, but lessthan all, of the fan speed settings are designated fan speed settings;(c) one of the fan speed settings is a designated fan speed setting; (d)none of the fan speed settings are designated fan speed settings; and(e) any particular fan speed setting(s) may be a designated fan speedsetting(s).

It should be appreciated that, in this example embodiment, the airfiltration device employs dynamic fan speed control when the current fanspeed setting is one of the at least one designated fan speed settingregardless of whether the air filtration device is operating in theautomatic fan speed setting selection operating mode or in one of themanual fan speed setting operating modes.

FIG. 27 illustrates a flowchart of one example embodiment of a dynamicfan speed control process or method 5000 of the present disclosure. Invarious embodiments, the dynamic fan speed control process 5000 isrepresented by a set of instructions stored in one or more memories andexecuted by the controller. Although the dynamic fan speed controlprocess 5000 is described with reference to the flowchart shown in FIG.27, it should be appreciated that many other processes of performing theacts associated with this illustrated dynamic fan speed control processmay be employed. For example, the order of certain of the illustratedblocks and/or diamonds may be changed, certain of the illustrated blocksand/or diamonds may be optional, and/or certain of the illustratedblocks and/or diamonds may not be employed.

The dynamic fan speed control process 5000 starts when the airfiltration device begins operating in either the automatic fan speedsetting selection operating mode or one of the manual fan speed settingoperating modes. The air filtration device determines the current fanspeed setting, as indicated by block 5100. As noted above, each fanspeed setting is associated with or corresponds to a desired air flowrate through the air filtration device. The air filtration devicedetermines if the current fan speed setting is the minimum fan speedsetting, as indicated by diamond 5110. If the air filtration devicedetermines that the current fan speed setting is the minimum fan speedsetting, the air filtration device sets the fan speed to a designatedfan speed, as indicated by block 5120.

The air filtration device determines if a fan speed determination timeinterval has elapsed, as indicated by diamond 5180. In this exampleembodiment, the fan speed determination time interval is 1 second,though it should be appreciated that any suitable time period may beemployed. If the air filtration device determines that the fan speeddetermination time interval has elapsed, the process 5000 returns to theblock 5100. If, on the other hand, the air filtration device determinesthat the fan speed determination time interval has not elapsed, the airfiltration device maintains the current fan speed, as indicated by block5190, and the process 5000 returns to the diamond 5180.

Returning to the diamond 5110, if the air filtration device determinesthat the current fan speed setting is not the minimum fan speed setting,the air filtration device determines the differential pressure (such asa pressure drop) across the fan using the fan differential pressuresensor, as indicated by block 5130. The air filtration device determinesa desired fan speed based at least in part on the differential pressureacross the fan and the desired air flow rate through the air filtrationdevice, as indicated by block 5140. The air filtration device determinesif the desired fan speed is greater than a maximum allowable speed ofthe fan, as indicated by diamond 5150.

If the air filtration device determines that the desired fan speed isgreater than the maximum allowable fan speed, the air filtration devicesets the fan speed to the maximum allowable fan speed, as indicated byblock 5160, and the process 5000 proceeds to the diamond 5180. If, onthe other hand, the air filtration device determines that the desiredfan speed is not greater than the maximum allowable fan speed, the airfiltration device sets the fan speed to the desired fan speed, asindicated by block 5170. The process 5000 proceeds to the diamond 5180.

It should be appreciated that, in this example embodiment, the airfiltration device determines the desired fan speed based at least inpart on the differential pressure across the fan and the desired airflow rate through the air filtration device and does not (directly) usethe pre-filter and HEPA filter occlusion levels (described below) to doso. In other words, in this example embodiment, the air filtrationdevice determines the desired fan speed is independent of and withoutdetermining the pre-filer and HEPA filter occlusion levels.

In other embodiments, the air filtration device determines the desiredfan speed based, at least in part, on the determined pre-filter and HEPAfilter occlusion levels. That is, in these embodiments the determinationof the desired fan speed directly depends on the determined pre-filterand HEPA filter occlusion levels.

In another embodiment, the air filtration device determines that a majorair filtration device malfunction occurs when the desired fan speedexceeds the maximum fan speed.

e. Filter Presence Detection

i. Pre-Filter Presence Detection

In this example embodiment, the air filtration device determines whetheran acceptable pre-filter is installed in the air filtration device usingthe pre-filter presence sensor, and prevents use of the fan when anacceptable pre-filter is not installed. FIG. 28 illustrates a flowchartof one example embodiment of a pre-filter presence detection process ormethod 6000 of the present disclosure. In various embodiments, thepre-filter presence detection process 6000 is represented by a set ofinstructions stored in one or more memories and executed by thecontroller. Although the pre-filter presence detection process 6000 isdescribed with reference to the flowchart shown in FIG. 28, it should beappreciated that many other processes of performing the acts associatedwith this illustrated pre-filter presence detection process may beemployed. For example, the order of certain of the illustrated blocksand/or diamonds may be changed, certain of the illustrated blocks and/ordiamonds may be optional, and/or certain of the illustrated blocksand/or diamonds may not be employed.

The pre-filter presence detection process 6000 starts when the airfiltration device receives a selection of one of the manual fan speedsetting selection operating modes or the automatic fan speed settingselection operating mode. As described above, in this exampleembodiment, the lower housing component supports or otherwise includes apre-filter limit switch that is actuatable by the pre-filter limitswitch actuator of the pre-filter. The air filtration device determineswhether the pre-filter limit switch is actuated, as indicated by diamond6100. If the air filtration device determines that the pre-filter limitswitch is actuated, the air filtration device determines that anacceptable pre-filter is installed, as indicated by block 6110, and theprocess 6000 proceeds to diamond 6140, described below. If, on the otherhand, the air filtration device determines that the pre-filter limitswitch is not actuated, the air filtration device indicates that anacceptable pre-filter is not installed, as indicated by block 6120, andthe air filtration device prevents use of the fan, as indicated by block6130. As indicated by the diamond 6140, once a pre-filter presencedetection time interval elapses, the process 6000 returns to the diamond6100. In this example embodiment, the pre-filter presence detection timeinterval is 1 second, though it should be appreciated that any suitableperiod of time may be employed.

In this example embodiment, the air filtration device indicates that anacceptable pre-filter is not installed by: (a) lighting the red LED ofthe pre-filter fault indicator, (b) lighting the LED of the airfiltration device status indicator red, and (c) outputting the filterfault indicator tone. It should be appreciated that any otherindications or combinations of indications may be employed instead of orin addition to the above-described indications.

In another embodiment, the air filtration device employs the pre-filterdifferential pressure sensor to determine whether an acceptablepre-filter is installed. In this embodiment, the air filtration devicedetermines the differential pressure across the pre-filter using thepre-filter differential pressure sensor. The air filtration devicedetermines if the differential pressure across the pre-filter is greaterthan or equal to a minimum allowable differential pressure across thepre-filter. If the air filtration device determines that thedifferential pressure across the pre-filter is greater than or equal tothe minimum allowable differential pressure across the pre-filter, theair filtration device determines that an acceptable pre-filter isinstalled. If, on the other hand, the air filtration device determinesthat the differential pressure across the pre-filter is less than (i.e.,not greater than or equal to) the minimum allowable differentialpressure across the pre-filter, the air filtration device indicates thatan acceptable pre-filter is not installed, and the air filtration deviceprevents use of the fan.

In another embodiment, the upper and lower edges of the pre-filter eachinclude an integrated metallic element (such as a 0.003 inch thick×1inch high element) that substantially spans the pre-filter'scircumference. In this embodiment, the pre-filter presence sensor is aHall Effect sensor that detects the metallic element. In thisembodiment, if the Hall Effect sensor does not detect any metallicelement, the air filtration device determines that an acceptablepre-filter is not installed and prevents use of the fan, and if the HallEffect sensor detects a metallic element, the air filtration devicedetermines that an acceptable pre-filter is installed.

In another embodiment, the pre-filter includes at least one RFID tag. Inthis embodiment, the pre-filter presence sensor is an RFID readerconfigured to read or recognize the RFID tag included in the pre-filter.In this embodiment, if the RFID reader does not read or recognize anRFID tag or reads or recognizes an improper RFID tag, the air filtrationdevice determines that an acceptable pre-filter is not installed, and ifthe RFID reader reads or recognizes a proper RFID tag, the airfiltration device determines that an acceptable pre-filter is installed.It should be appreciated that any other suitable pre-filter presencedetection process may be employed.

ii. HEPA Filter Presence Detection

In this example embodiment, the air filtration device determines whetheran acceptable HEPA filter is installed in the air filtration deviceusing the differential pressure across the HEPA filter, and prevents useof the fan when an acceptable HEPA filter is not installed. FIG. 29illustrates a flowchart of one example embodiment of a HEPA filterpresence detection process or method 7000 of the present disclosure. Invarious embodiments, the HEPA filter presence detection process 7000 isrepresented by a set of instructions stored in one or more memories andexecuted by the controller. Although the HEPA filter presence detectionprocess 7000 is described with reference to the flowchart shown in FIG.29, it should be appreciated that many other processes of performing theacts associated with this illustrated HEPA filter presence detectionprocess may be employed. For example, the order of certain of theillustrated blocks and/or diamonds may be changed, certain of theillustrated blocks and/or diamonds may be optional, and/or certain ofthe illustrated blocks and/or diamonds may not be employed.

The HEPA filter presence detection process 7000 starts when the airfiltration device receives a selection of one of the manual fan speedsetting selection operating modes or the automatic fan speed settingselection operating mode. The air filtration device determines thedifferential pressure (such as a pressure drop) across the HEPA filterusing the HEPA filter differential pressure sensor, as indicated byblock 7100. The air filtration device determines if the differentialpressure across the HEPA filter is greater than or equal to a minimumallowable differential pressure across the HEPA filter, as indicated bydiamond 7110. If the air filtration device determines that thedifferential pressure across the HEPA filter is greater than or equal tothe minimum allowable differential pressure across the HEPA filter, theair filtration device determines that an acceptable HEPA filter isinstalled, as indicated by block 7120, and the process 7000 proceeds todiamond 7150, described below.

If, on the other hand, the air filtration device determines that thedifferential pressure across the HEPA filter is less than (i.e., notgreater than or equal to) the minimum allowable differential pressureacross the HEPA filter, the air filtration device indicates that anacceptable HEPA filter is not installed, as indicated by block 7130, andthe air filtration device prevents use of the fan, as indicated by block7140. As indicated by the diamond 7150, once a HEPA filter presencedetection time interval elapses, the process 7000 returns to the block7100.

In this example embodiment, the HEPA filter presence detection timeinterval is 1 hour, though it should be appreciated that any suitableperiod of time may be employed. Additionally, in this exampleembodiment, the minimum allowable differential pressure across the HEPAfilter is equal to the differential pressure across 0.10 inches of waterat a fan speed of 3,000 revolutions per minute, though it should beappreciated that any suitable minimum allowable differential pressureacross the HEPA filter may be employed.

In this example embodiment, the air filtration device indicates that anacceptable HEPA filter is not installed by: (a) lighting the red LED ofthe HEPA filter fault indicator, (b) lighting the LED of the airfiltration device status indicator red, and (c) outputting the filterfault indicator tone. It should be appreciated that any otherindications or combinations of indications may be employed instead of orin addition to the above-described indications.

In another embodiment, the HEPA filter includes one or more integratedhollow pressure tubes positioned vertically among the pleats of the HEPAfilter media. An end of each of these pressure tubes is flush with thebottom of the lower HEPA filter end cap. In this embodiment, the airfiltration device includes one or more pressure sensors configured todetect the presence of the pressure tubes. Thus, in this embodiment, ifa HEPA filter without such pressure tubes is installed, the airfiltration device will determine that an improper HEPA filter isinstalled, and will not operate.

In another embodiment, the HEPA filter includes at least one RFID tag.In this embodiment, the air filtration device includes a HEPA filterpresence sensor in the form of an RFID reader configured to read orrecognize the RFID tag included in the HEPA filter. In this embodiment,if the RFID reader does not read or recognize an RFID tag or reads orrecognizes an improper RFID tag, the air filtration device determinesthat an acceptable HEPA filter is not installed, and if the RFID readerreads or recognizes a proper RFID tag, the air filtration devicedetermines that an acceptable HEPA filter is installed. It should beappreciated that any other suitable HEPA filter presence detectionprocess may be employed.

As described below, in certain embodiments, the HEPA filter presencedetection process is part of the filter occlusion level monitoringprocess.

f. Filter Occlusion Level Monitoring

In this example embodiment, the air filtration device monitors theocclusion levels of the pre-filter and the HEPA filter (i.e., thecleanliness levels of the pre-filter and the HEPA filter) and providesfeedback regarding the filter occlusion levels to the user to enable theuser to quickly and easily determine how clean (or dirty, blocked, orclogged) the pre-filter and the HEPA filter are. When the pre-filterocclusion level exceeds a pre-filter shutdown threshold, the HEPA filterocclusion level exceeds a HEPA filter shutdown threshold, or both, theair filtration device enters a shutdown mode in which the air filtrationdevice eventually prevents any use of the fan until the appropriatefilter(s) is(are) replaced. This ensures that the air filtration devicedoes not operate for an extended period of time with a pre-filter and/ora HEPA filter so occluded as to inhibit effective and efficientoperation of the air filtration device.

FIG. 30 illustrates a flowchart of one example embodiment of a filterocclusion level monitoring process or method 8000 of the presentdisclosure. In various embodiments, the filter occlusion levelmonitoring process 8000 is represented by a set of instructions storedin one or more memories and executed by t. Although the filter occlusionlevel monitoring process 8000 is described with reference to theflowchart shown in FIG. 30, it should be appreciated that many otherprocesses of performing the acts associated with this illustrated filterocclusion level monitoring process may be employed. For example, theorder of certain of the illustrated blocks and/or diamonds may bechanged, certain of the illustrated blocks and/or diamonds may beoptional, and/or certain of the illustrated blocks and/or diamonds maynot be employed.

The filter occlusion level monitoring process 8000 starts after (such asa designated period of time after (such as 10 seconds or any othersuitable time period)) the air filtration device receives a selection ofthe automatic fan speed setting selection operating mode or any of themanual fan speed setting operating modes either upon power-up of the airfiltration device or when the air filtration device is in the fullstandby mode (described above). The air filtration device increases thefan speed to a differential pressure determination fan speed, such as3,000 revolutions per minute or any other suitable fan speed, asindicated by block 8105. The air filtration device determines thedifferential pressure (such as a pressure drop) across the pre-filterusing the pre-filter differential pressure sensor, as indicated by block8100, and the differential pressure (such as a pressure drop) across theHEPA filter using the HEPA filter differential pressure sensor, asindicated by block 8110.

The air filtration device determines the pre-filter occlusion levelbased, at least in part, on the determined differential pressure acrossthe pre-filter and the determined differential pressure across the HEPAfilter, as indicated by block 8120. The air filtration device alsodetermines the HEPA filter occlusion level based, at least in part, onthe on the determined differential pressure across the pre-filter andthe determined differential pressure across the HEPA filter, asindicated by block 8160. In this example embodiment, while determiningthe filter occlusion levels (which includes determining the differentialpressures across the pre-filter and the HEPA filter), the air filtrationdevice: (a) lights the yellow LED of the pre-filter status indicators ina blinking or flashing manner; (b) lights the yellow LED of the HEPAfilter status indicators in a blinking or flashing manner; and (c)displays “tESt” in the hour meter display. This enables the user toquickly and easily determine when the air filtration device is measuringthe filter occlusion levels. It should be appreciated that any otherindications or combinations of indications may be employed instead of orin addition to the above-described indications.

The air filtration device determines if the determined pre-filterocclusion level exceeds a pre-filter shutdown threshold, as indicated bydiamond 8130. The pre-filter shutdown threshold is a maximum allowablepre-filter occlusion level. Once the pre-filter occlusion level reachesthe pre-filter shutdown threshold, the air filtration device may nolonger efficiently and effectively clean the air (until the pre-filteris replaced). If the air filtration device determines that thedetermined pre-filter occlusion level exceeds the pre-filter shutdownthreshold, the process 8000 proceeds to diamond 8200, described below.

If, on the other hand, the air filtration device determines that thedetermined pre-filter occlusion level does not exceed the pre-filtershutdown threshold, the air filtration device determines which of aplurality of different pre-filter occlusion level ranges includes thedetermined pre-filter occlusion level, as indicated by block 8140. Inthis example embodiment, each pre-filter occlusion level range isassociated with a general indicator of the cleanliness of thepre-filter. For instance, in this example embodiment, the pre-filterocclusion level ranges include: (a) a first or Clean pre-filterocclusion level range, (b) a second or Slightly Occluded pre-filterocclusion level range, and (c) a third or Highly Occluded pre-filterocclusion level range. In this example embodiment, each occlusion levelincluded in the Slightly Occluded pre-filter occlusion level range isgreater than each occlusion level included in the Clean pre-filterocclusion level range, and each occlusion level included in the HighlyOccluded pre-filter occlusion level range is greater than each occlusionlevel included in the Slightly Occluded pre-filter occlusion levelrange. The maximum occlusion level in the Highly Occluded pre-filterocclusion level range is the pre-filter shutdown threshold. Forinstance, Table 3 below includes example ranges of occlusion levelsassociated with the Clean, Slightly Occluded, and Highly Occludedpre-filter occlusion level ranges. In this example, the occlusion levelsrange from zero to ten. It should be appreciated that each cleanlinessindicator may be associated with any suitable range of pre-filterocclusion levels, and that each range of pre-filter occlusion levels mayinclude any suitable pre-filter occlusion levels.

TABLE 3 Example Occlusion Levels Associated With Example Pre-FilterOcclusion Level Ranges Cleanliness Indicator Range of Pre-FilterOcclusion Levels Clean 0 to 2 Slightly Occluded 3 to 5 Highly Occluded 6to pre-filter shutdown threshold

Returning to the process 8000, the air filtration device indicates thepre-filter occlusion level range that includes the determined pre-filterocclusion level, as indicated by block 8150. In this example embodiment,the air filtration device does so by: (a) if the Clean pre-filterocclusion level range includes the determined pre-filter occlusionlevel, lighting the green LED of the pre-filter status indicators; (b)if the Slightly Occluded pre-filter occlusion level range includes thedetermined pre-filter occlusion level, lighting the yellow LED of thepre-filter status indicators; and (c) if the Highly Occluded pre-filterocclusion level range includes the determined pre-filter occlusionlevel, lighting the red LED of the pre-filter status indicators. Thisenables a user to quickly and easily determine how clean (or dirty) thepre-filter is. The process 8000 proceeds to the diamond 8200.

Turning to diamond 8170, the air filtration device determines if thedetermined HEPA filter occlusion level exceeds a HEPA filter shutdownthreshold. The HEPA filter shutdown threshold is a maximum allowableHEPA filter occlusion level. Once the HEPA filter occlusion levelreaches the HEPA filter shutdown threshold, the air filtration devicemay no longer efficiently and effectively clean the air (until the HEPAfilter is replaced). If the air filtration device determines that thedetermined HEPA filter occlusion level exceeds the HEPA filter shutdownthreshold, the process 8000 proceeds to the diamond 8200, describedbelow.

If, on the other hand, the air filtration device determines that thedetermined HEPA filter occlusion level does not exceed the HEPA filtershutdown threshold, the air filtration device determines which of aplurality of different HEPA filter occlusion level ranges includes thedetermined HEPA filter occlusion level, as indicated by block 8180. Inthis example embodiment, each HEPA filter occlusion level range isassociated with a general indicator of the cleanliness of the HEPAfilter. For instance, in this example embodiment, the HEPA filterocclusion level ranges include: (a) a first or Clean HEPA filterocclusion level range, (b) a second or Slightly Occluded HEPA filterocclusion level range, and (c) a third or Highly Occluded HEPA filterocclusion level range. In this example embodiment, each occlusion levelincluded in the Slightly Occluded HEPA filter occlusion level range isgreater than each occlusion level included in the Clean HEPA filterocclusion level range, and each occlusion level included in the HighlyOccluded HEPA filter occlusion level range is greater than eachocclusion level included in the Slightly Occluded HEPA filter occlusionlevel range. The maximum occlusion level in the Highly Occluded HEPAfilter occlusion level range is the HEPA filter shutdown threshold. Forinstance, Table 4 below includes example ranges of occlusion levelsassociated with the Clean, Slightly Occluded, and Highly Occluded HEPAfilter occlusion level ranges. In this example, the occlusion levelsrange from zero to ten. It should be appreciated that each cleanlinessindicator may be associated with any suitable range of HEPA filterocclusion levels, and that each range of HEPA filter occlusion levelsmay include any suitable HEPA filter occlusion levels.

TABLE 4 Example Occlusion Levels Associated With Example HEPA filterOcclusion Level Ranges Cleanliness Indicator Range of HEPA FilterOcclusion Levels Clean 0 to 2 Slightly Occluded 3 to 5 Highly Occluded 6to HEPA filter shutdown threshold

Returning to the process 8000, the air filtration device indicates theHEPA filter occlusion level range that includes the determined HEPAfilter occlusion level, as indicated by block 8190. In this exampleembodiment, the air filtration device does so by: (a) if the Clean HEPAfilter occlusion level range includes the determined HEPA filterocclusion level, lighting the green LED of the HEPA filter statusindicators; (b) if the Slightly Occluded HEPA filter occlusion levelrange includes the determined HEPA filter occlusion level, lighting theyellow LED of the HEPA filter status indicators; and (c) if the HighlyOccluded HEPA filter occlusion level range includes the determined HEPAfilter occlusion level, lighting the red LED of the HEPA filter statusindicators. This enables a user to quickly and easily determine howclean (or dirty) the HEPA filter is. The process 8000 proceeds to thediamond 8200.

Turning to the diamond 8200, the air filtration device determines if:(a) the determined pre-filter occlusion level exceeds the pre-filtershutdown threshold, and/or (b) the determined HEPA filter occlusionlevel exceeds the HEPA filter shutdown threshold. If neither: (a) thedetermined pre-filter occlusion level exceeds the pre-filter shutdownthreshold, nor (b) the determined HEPA filter occlusion level exceedsthe HEPA filter shutdown threshold, as indicated by diamond 8210, once afilter occlusion level determination time interval elapses, the process8000 returns to the block 8100. In this example embodiment, the filterocclusion level determination time interval is 60 minutes, though itshould be appreciated that any suitable period of time may be employed.

If, on the other hand, at least one of: (a) the determined pre-filterocclusion level exceeds the pre-filter shutdown threshold, and (b) thedetermined HEPA filter occlusion level exceeds the HEPA filter shutdownthreshold, the air filtration device indicates that the pre-filter, theHEPA filter, or both need replacement, as indicated by block 8220. Morespecifically: (a) if the determined pre-filter occlusion level exceedsthe pre-filter shutdown threshold, the air filtration device indicatesthat the pre-filter needs replacement; (b) if the determined HEPA filterocclusion level exceeds the HEPA filter shutdown threshold, the airfiltration device indicates that the HEPA filter needs replacement; and(c) if the determined pre-filter occlusion level exceeds the pre-filtershutdown threshold and the determined HEPA filter occlusion levelexceeds the HEPA filter shutdown threshold, the air filtration deviceindicates that both the pre-filter and the HEPA filter need replacement.The air filtration device enters the shutdown mode, as indicated byblock 8230, and initiates a designated shutdown time period, asindicated by block 8240. In this example embodiment, the designatedshutdown time period is 4 hours, though it should be appreciated thatthe designated shutdown time period may be any suitable time period.

The air filtration device determines if it is operating in the automaticfan speed setting selection operating mode or the manual maximum fanspeed setting operating mode, as indicated by diamond 8250. If the airfiltration device is not operating in either the automatic fan speedsetting selection operating mode or the manual maximum fan speed settingoperating mode, the process 8000 proceeds to block 8270, describedbelow. If, on the other hand, the air filtration device is operating inthe automatic fan speed setting selection operating mode or the manualmaximum fan speed setting operating mode, the air filtration devicepowers down the fan, as indicated by block 8260.

The air filtration device prevents use of the automatic fan speedsetting selection operating mode and prevents use of the manual maximumfan speed setting operating mode, as indicated by the block 8270. Theair filtration device enables operation of the air filtration device ineither the manual medium fan speed setting operating mode or the manualminimum fan speed setting operating mode, as indicated by block 8280.The air filtration device determines if the designated shutdown timeperiod has expired, as indicated by diamond 8290. If the air filtrationdevice determines that the designated shutdown time period has notexpired, the process 8000 returns to the block 8280. If, on the otherhand, the air filtration device determines that the designated shutdowntime period has expired, the air filtration device powers down the fan,as indicated by block 8300, and prevents use of the fan, as indicated byblock 8310. In other words, once the designated shutdown time periodexpires, the air filtration device prevents use of the automatic fanspeed setting selection operating mode and any of the manual fan speedsetting operating modes.

In this example embodiment, the air filtration device indicates that thepre-filter, the HEPA filter, or both need replacement in a variety ofdifferent manners. More specifically, in this example embodiment, if thepre-filter occlusion level exceeds the pre-filter shutdown threshold andthe air filtration device is operating in the automatic fan speedsetting selection operating mode or the manual maximum fan speed settingoperating mode, the air filtration device indicates that the pre-filterneeds replacement by: (a) lighting the red LED of the pre-filter statusindicators in a flashing or blinking manner, (b) lighting the red LED ofthe pre-filter fault indicator, (c) lighting the LED of the airfiltration device status indicator red, and (d) outputting the filterchange alarm tone. In this example embodiment, if the pre-filterocclusion level exceeds the pre-filter shutdown threshold and the airfiltration device is operating in the manual medium fan speed settingoperating mode or the manual minimum fan speed setting mode, the airfiltration device indicates that the pre-filter needs replacement by:(a) lighting the red LED of the pre-filter status indicators in aflashing or blinking manner, (b) lighting the red LED of the pre-filterfault indicator, and (c) lighting the LED of the air filtration devicestatus indicator green or keeping the LED of the air filtration devicestatus indicator lit green. When the designated shutdown time periodexpires, the air filtration device: (a) lights the LED of the airfiltration device status indicator red, and (b) outputs the filterchange alarm tone while maintaining flashing the red pre-filter statusindicator and lighting the red LED of the pre-filter fault indicator.

In this example embodiment, if the HEPA filter occlusion level exceedsthe HEPA filter shutdown threshold and the air filtration device isoperating in the automatic fan speed setting selection operating mode orthe manual maximum fan speed setting operating mode, the air filtrationdevice indicates that the HEPA filter needs replacement by: (a) lightingthe red LED of the HEPA filter status indicators in a flashing orblinking manner, (b) lighting the red LED of the HEPA filter faultindicator, (c) lighting the LED of the air filtration device statusindicator red, and (d) outputting the filter change alarm tone. In thisexample embodiment, if the HEPA filter occlusion level exceeds the HEPAfilter shutdown threshold and the air filtration device is operating inthe manual medium fan speed setting operating mode or the manual minimumfan speed setting mode, the air filtration device indicates that theHEPA filter needs replacement by: (a) lighting the red LED of the HEPAfilter status indicators in a flashing or blinking manner, (b) lightingthe red LED of the HEPA filter fault indicator, and (c) lighting the LEDof the air filtration device status indicator green or keeping the LEDof the air filtration device status indicator lit green. When thedesignated shutdown time period expires, the air filtration device: (a)lights the LED of the air filtration device status indicator red, and(b) outputs the filter change alarm tone while maintaining flashing thered HEPA filter status indicator and lighting the red LED of the HEPAfilter fault indicator.

In this example embodiment, if the air filtration device receives aninput to switch to the standby mode while the air filtration device isdetermining the pre-filter and HEPA filter occlusion levels, the airfiltration device stops such determinations and shuts the fan down. Theair filtration device restarts the filter occlusion level monitoringprocess once the air filtration device receives an input to switch fromthe standby mode into the automatic fan speed setting selectionoperating mode or any of the manual fan speed setting operating modes.

Further, in this example embodiment, if the air filtration devicereceives an input to switch from one of: (a) the automatic fan speedsetting selection operating mode, and (b) one of the manual fan speedsetting operating modes to another one of: (a) the automatic fan speedsetting selection operating mode, and (b) one of the manual fan speedsetting operating modes while the air filtration device is determiningthe pre-filter and HEPA filter occlusion levels, the air filtrationdevice ignores this input until the determinations are complete. Forinstance, if the air filtration device receives an input to switch theair filtration device from the manual medium fan speed setting operatingmode to the manual maximum fan speed setting operating mode while theair filtration device is determining the pre-filter and HEPA filterocclusion levels, the air filtration device does not switch from themanual medium fan speed setting operating mode to the manual maximum fanspeed setting operating mode until such determinations are complete.

In another embodiment, the air filtration device prevents use of the fanonce at least one of: (a) the determined pre-filter occlusion levelexceeds the pre-filter shut down threshold, and (b) the determined HEPAfilter occlusion level exceeds the HEPA filter shut down threshold. Thatis, in this embodiment, the air filtration device does not enableoperation at any of the fan speed settings once the air filtrationdevice determines that at least one of the filters needs replacement.

As noted above, in certain embodiments, the HEPA filter presencedetection process is part of the filter occlusion level monitoringprocess. For instance, in one example embodiment, after determining thedifferential pressure across the HEPA filter using the HEPA filterdifferential pressure sensor (such as indicated by block 8110 of FIG.30A), the air filtration device determines if the differential pressureacross the HEPA filter is greater than a minimum allowable differentialpressure across the HEPA filter (such as indicated by diamond 7110 ofFIG. 29). If the air filtration device determines that the differentialpressure across the HEPA filter is greater than the minimum allowabledifferential pressure across the HEPA filter, the air filtration devicedetermines that an acceptable HEPA filter is installed (such asindicated by block 7120 of FIG. 29) and proceeds to determine thepre-filter and HEPA filter occlusion levels (such as indicated by blocks8120 and 8160 of FIG. 30A) and the rest of the filter occlusion levelmonitoring process. If, on the other hand, the air filtration devicedetermines that the differential pressure across the HEPA filter is notgreater than the minimum allowable differential pressure across the HEPAfilter, the air filtration device indicates than an acceptable HEPAfilter is not installed (such as indicated by block 7130 of FIG. 29),prevents use of the fan (such as indicated by block 7140 of FIG. 29),and terminates the filter occlusion level monitoring process and theHEPA filter presence detection process.

g. Air Filtration Device Malfunctions

In this example embodiment, the air filtration device monitors for aplurality of different major air filtration device malfunctions, such as(but not limited to): (a) a locked fan motor; (b) disconnecteddifferential pressure sensor tubes; (c) disconnected electroniccomponents (e.g., the fan, the operating mode selector, and the like);and (d) an electronics failure (e.g., an hour meter display failure or apre-filter status indicator failure). In this example embodiment, if theair filtration device determines that one of the major air filtrationdevice malfunctions occurs, the air filtration device: (a) powers downthe fan, (b) lights the LED of the air filtration device statusindicator red, and (c) outputs the audible major air filtration devicemalfunction tone.

In this example embodiment, the air filtration device also monitors fordust sensor failure. If the air filtration device determines that thedust sensor fails, the air filtration device: (a) enables operation ofthe air filtration device in any of the manual fan speed settingoperating modes; and (b) if the automatic fan speed setting selectionoperating mode is selected, indicates that a major air filtration devicemalfunctions occurs, as described above.

It should be understood that modifications and variations may beeffected without departing from the scope of the novel concepts of thepresent disclosure, and it should be understood that this application isto be limited only by the scope of the appended claims.

The invention is claimed as follows:
 1. An air filtration devicecomprising: a housing including a lower housing component and a lockingcover removably attachable to the lower housing component, the lowerhousing component configured to receive a removable exterior pre-filterand a separately removable inner high-efficiency particulate air filter;a fan assembly including a fan, the fan assembly mounted within a fanassembly mounting chamber defined by the lower housing component; and aprocessor configured to control a speed of the fan such that a rate ofair flow through the air filtration device when the air filtrationdevice is operating is within a target range and to stop the fan if therate of air flow through the air filtration device when the airfiltration device is operating cannot be sustained within the targetrange.
 2. The air filtration device of claim 1, wherein the lowerhousing is configured mate with a lower end cap of the removable innerhigh-efficiency particulate air filter.
 3. The air filtration device ofclaim 2, wherein the locking cover is configured mate with an upper endcap of the removable inner high-efficiency particulate air filter. 4.The air filtration device of claim 1, wherein the locking cover isconfigured mate with an upper end cap of the removable innerhigh-efficiency particulate air filter.
 5. The air filtration device ofclaim 1, wherein the lower housing is configured to be engaged by apre-filter sensor triggering component of the removable exteriorpre-filter.
 6. The air filtration device of claim 1, wherein theprocessor is configured to prevent operation of the air filtrationdevice in response to the removable exterior pre-filter not beingpositioned in the lower housing.
 7. An air filtration device comprising:a housing including: (a) a lower housing component including a base, aplurality of stabilizers extending upwardly from the base, the lowerhousing component configured to receive a removable exterior pre-filterand a separately removable inner high-efficiency particulate air filter;(b) a locking cover removably attachable to the stabilizers; and (c) afan assembly mounting chamber defined by an underside of the lowerhousing component; a fan assembly mounted within the fan assemblymounting chamber; and a fan assembly mounting chamber cover removablyattachable to the underside of the lower housing component; and anexhaust port extending transversely and radially outward from the baseand defining an exhaust channel.
 8. The air filtration device of claim7, wherein the lower housing is configured mate with a lower end cap ofthe removable inner high-efficiency particulate air filter.
 9. The airfiltration device of claim 8, wherein the locking cover is configuredmate with an upper end cap of the removable inner high-efficiencyparticulate air filter.
 10. The air filtration device of claim 7,wherein the locking cover is configured mate with an upper end cap ofthe removable inner high-efficiency particulate air filter.
 11. The airfiltration device of claim 7, wherein the lower housing is configured tobe engaged by a pre-filter sensor triggering component of the removableexterior pre-filter.
 12. The air filtration device of claim 7, whereinthe processor is configured to prevent operation of the air filtrationdevice in response to the removable exterior pre-filter not beingpositioned in the lower housing.
 13. An air filtration devicecomprising: a housing including: (a) a lower housing component includinga base, a plurality of stabilizers extending upwardly from the base,wherein each of the stabilizers includes a latch, the lower housingcomponent configured to receive a removable exterior pre-filter and aseparately removable inner high-efficiency particulate air filter; (b) alocking cover removably attachable to the stabilizers, each latchconfigured to engage the locking cover; and (c) a fan assembly mountingchamber defined by an underside of the lower housing component; a fanassembly mounted within the fan assembly mounting chamber; a fanassembly mounting chamber cover removably attachable to the underside ofthe lower housing component; and an exhaust port extending transverselyfrom the base.
 14. The air filtration device of claim 13, wherein thelower housing is configured mate with a lower end cap of the removableinner high-efficiency particulate air filter.
 15. The air filtrationdevice of claim 14, wherein the locking cover is configured mate with anupper end cap of the removable inner high-efficiency particulate airfilter.
 16. The air filtration device of claim 13, wherein the lockingcover is configured mate with an upper end cap of the removable innerhigh-efficiency particulate air filter.
 17. The air filtration device ofclaim 13, wherein the lower housing is configured to be engaged by apre-filter sensor triggering component of the removable exteriorpre-filter.
 18. The air filtration device of claim 13, wherein theprocessor is configured to prevent operation of the air filtrationdevice in response to the removable exterior pre-filter not beingpositioned in the lower housing.